Dear Stockholders of Banc of California, Inc. and Shareholders of Pacific Mercantile Bancorp:

Sincerely,

Both Banc of California, Inc. and Pacific Mercantile Bancorp, which we refer to as BOC and PMB, respectively, file annual, quarterly and current reports, proxy statements and other business and financial information with the Securities and Exchange Commission, referred to as the SEC. You can read the SEC filings of BOC and PMB over the Internet at the SEC’s website at www.sec.gov. You may also obtain these documents, free of charge, from BOC at www.bancofcal.com under the “Investor Relations” link and then under the “Financials and Filings” tab or from PMB at www.pmbank.com under the heading “Investors Relations” and then under the tab “SEC Filings.”

BOC has filed a registration statement on Form S-4 of which this document forms a part. As permitted by SEC rules, this document does not contain all of the information included in the registration statement or in the exhibits or schedules to the registration statement. You may read and copy the registration statement, including any amendments, schedules and exhibits, at the addresses set forth below. Statements contained in this document as to the contents of any contract or other documents referred to in this document are not necessarily complete. In each case, you should refer to the copy of the applicable contract or other document filed as an exhibit to the registration statement. This document incorporates by reference documents that BOC and PMB have previously filed with the SEC. They contain important information about the companies and their financial condition. For more information, please see the section entitled “Incorporation of Certain Documents by Reference.” These documents are available without charge to you upon written or oral request to the applicable company’s principal executive offices. The respective addresses and telephone numbers of such principal executive offices are listed below.

To obtain timely delivery of these documents, BOC stockholders must request the information no later than Wednesday, June 16, 2021 in order to receive it before the BOC special meeting and PMB shareholders must request the information no later than Wednesday, June 16, 2021 in order to receive it before the PMB special meeting.

BOC common stock is traded on the NYSE under the symbol “BANC,” and PMB common shares are traded on Nasdaq under the symbol “PMBC.”

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Banc of California, Inc., referred to as BOC, will be held virtually, solely by means of remote communication, at http://www.virtualshareholdermeeting.com/BANC2021SM, on Wednesday, June 23, 2021, at 8:00 a.m., local time for the purpose of considering and voting upon the following proposals:

BOC will transact no other business at the BOC special meeting other than as listed above.

The BOC board of directors has set Monday, May 10, 2021 as the record date for the BOC special meeting. Only holders of record of BOC voting common stock at the close of business on Monday, May 10, 2021 will be entitled to notice of and to vote at the BOC special meeting and any adjournments or postponements thereof.

Stockholder approval of the BOC merger proposal by the affirmative vote of a majority of the outstanding stock entitled to vote and of the BOC stock issuance proposal by the affirmative vote of a majority of the votes cast at a duly held meeting at which there is a quorum is required to complete the merger.

The BOC board of directors has approved the merger and the issuance of BOC common stock in connection with the merger and recommends that you vote “FOR” the BOC merger proposal, “FOR” the BOC stock issuance proposal and “FOR” the BOC adjournment proposal.

Your vote is very important. To ensure your representation at the BOC special meeting, please (1) complete, sign, date and return the enclosed proxy card in the envelope provided or (2) follow the instructions provided on the proxy card to submit your proxy by telephone or through the Internet. If you hold your shares of BOC common stock through a bank, broker or other nominee, you should direct the vote of your shares in accordance with the voting instructions received from your bank, broker or other nominee. Please vote promptly whether or not you expect to attend the BOC special meeting.

Due to the continuing public health impact of the COVID-19 pandemic and to support the well-being of our stockholders and employees, we are holding the BOC special meeting virtually via webcast. No physical meeting will be held. Stockholders of record as of the record date who have a control number may attend the BOC special meeting and may vote during, and participate in, the BOC special meeting by visiting http://www.virtualshareholdermeeting.com/BANC2021SM. Online access to the BOC special meeting, which will be an audio-only webcast, will begin at 7:45 a.m., local time, on Wednesday, June 23, 2021. For registered stockholders, the control number can be found on your proxy card. Stockholders who hold shares through a bank, broker or other nominee must obtain a legal proxy from their bank, broker or other nominee and register in advance to be able to attend the BOC special meeting and vote during, and participate in, the BOC special meeting. Stockholders should follow the instructions provided by their respective bank, broker or other nominee to participate in the BOC special meeting.

Please read carefully the sections in the joint proxy statement/prospectus regarding attending and voting at the BOC special meeting to ensure that you comply with these requirements. You are encouraged to read the entire joint proxy statement/prospectus, including the appendices and the documents incorporated by reference, carefully. If you have any questions about the proposals or need assistance in voting your shares, please call BOC Investor Relations at (855) 361-2262.

BY ORDER OF THE BOARD OF DIRECTORS

NOTICE IS HEREBY GIVEN that a special meeting of the shareholders of Pacific Mercantile Bancorp, referred to as PMB, will be held in the first floor Training Room at PMB’s offices at 949 South Coast Drive, Costa Mesa, California 92626, on Wednesday, June 23, 2021, at 9:00 a.m., local time for the purpose of considering and voting upon the following proposals:

PMB will transact no other business at the PMB special meeting other than as listed above.

The PMB board of directors has set Monday, May 10, 2021 as the record date for the PMB special meeting. Only holders of record of PMB voting common shares at the close of business on Monday, May 10, 2021 will be entitled to notice of and to vote at the PMB special meeting and any adjournments or postponements thereof.

Shareholder approval of the PMB merger proposal by the affirmative vote of a majority of the outstanding shares entitled to vote is required to complete the merger.

The PMB board of directors has approved the merger agreement and the transactions contemplated thereby and recommends that you vote “FOR” the PMB merger proposal, “FOR” the PMB NEO compensation proposal and “FOR” the PMB adjournment proposal.

Your vote is very important. To ensure your representation at the PMB special meeting, please (1) complete, sign, date and return the enclosed proxy card in the envelope provided or (2) follow the instructions provided on the proxy card to submit your proxy by telephone or through the Internet. If you hold your shares through a bank, broker or other nominee, you should direct the vote of your shares in accordance with the voting instructions received from your bank, broker or other nominee. Please vote promptly whether or not you expect to attend the PMB special meeting.

We expect to hold the PMB special meeting in person, but we continue to monitor the situation regarding COVID-19 closely. Accordingly, we are planning for the possibility that the PMB special meeting may be subject to special precautions, including limitations on the number of participants in one room or other limitations. In that regard, only PMB shareholders will be admitted to the PMB special meeting. No guests will be permitted. For safety and security purposes, you will need to obtain authorization in advance to attend the PMB special meeting in person. To do so, please make your request by mail to PMB at 949 South Coast Drive, Costa Mesa, CA 92626, Attention: Chief Financial Officer, by email at Curt.Christianssen@pmbank.com or by phone at (714) 438-2500. PMB must receive your request for pre-authorization on or before Tuesday, June 15, 2021.

Please read carefully the sections in the joint proxy statement/prospectus regarding attending and voting at the PMB special meeting to ensure that you comply with these requirements. You are encouraged to read the entire joint proxy statement/prospectus, including the appendices and the documents incorporated by reference, carefully. If you have any questions about the proposals or need assistance in voting your shares, please call PMB Investor Relations at (714) 438-2531.

BY ORDER OF THE BOARD OF DIRECTORS

The following questions and answers briefly address certain commonly asked questions about the merger and the respective special meetings of stockholders of Banc of California, Inc. and shareholders of Pacific Mercantile Bancorp. You should carefully read the remainder of this document because the information in this section may not provide all the information that might be important to you in determining how to vote. Additional important information is also contained in the appendices to, and the documents incorporated by reference in, this document.

The merger cannot be completed unless BOC stockholders approve the merger and the issuance of BOC common stock in connection with the merger and PMB shareholders approve the principal terms of the merger agreement. Each of BOC and PMB is holding a special meeting of its stockholders or shareholders, respectively, to vote on the proposals necessary to complete the merger as well as other related matters. Information about the special meetings, the merger and the other business to be considered at the special meetings is contained in this document.

This document constitutes both a joint proxy statement of BOC and PMB and a prospectus of BOC. It is a joint proxy statement because each of the board of directors of BOC and PMB is soliciting proxies from their respective stockholders and shareholders. It is a prospectus because BOC, in connection with the merger, is offering shares of its common stock in exchange for outstanding PMB common shares in the merger.

This 20 consecutive trading day average price is referred to as the BOC average closing price; the fifth business day immediately prior to the closing date is referred to as the determination date; and the 20 consecutive trading day period ending on the determination date is referred to as the determination period.

Based on the closing price of BOC common stock on March 22, 2021, the last trading day before the public announcement of the merger agreement, the value of the per share merger consideration payable to holders

of PMB common shares was $9.77. Based on the closing price of BOC common stock on May 10, 2021, the last practicable date before the date of this document, the value of the per share merger consideration payable to holders of PMB common shares was $8.86.

PMB Restricted Shares and RSUs. At the effective time of the merger, each outstanding award of PMB restricted stock, referred to as the PMB restricted shares, and each outstanding award of PMB restricted stock units, referred to as PMB RSUs, will, automatically and without any action on the part of the holder of such PMB restricted shares or PMB RSUs, accelerate in full, be cancelled and will only entitle the holder of such PMB restricted shares or PMB RSUs to receive, on the first regular payroll date following the closing date of the merger, an amount in cash equal to the product of (i) such holder’s total number of PMB restricted shares or RSUs, as applicable, and (ii) an amount equal to the product of the BOC average closing price and 0.50, less any applicable taxes required to be withheld with respect to such vesting, which tax withholding may, at the election of the holder, be effected by deduction from such cash amount equal to the amount of taxes to be withheld.

PMB Special Meeting: Holders of record of PMB voting common shares at the close of business on Monday, May 10, 2021, which is the date that the PMB board of directors has fixed as the record date for the PMB special meeting, are entitled to vote at the PMB special meeting.

PMB Special Meeting: A majority of the shares entitled to vote, represented in person or by proxy, constitutes a quorum for transacting business at the PMB special meeting. Proxies marked as abstaining on any matter to be acted upon by shareholders will be treated as present at the meeting for purposes of determining the presence or absence of a quorum.

Stockholder approval of the BOC merger proposal and the BOC stock issuance proposal, referred to as the BOC stockholder approval, is required to complete the merger. BOC will transact no business at the BOC special meeting other than as listed above.

PMB Special Meeting: PMB shareholders are being asked to vote on the following proposals:

Shareholder approval of the PMB merger proposal, referred to as the PMB shareholder approval, is required to complete the merger. PMB will transact no business at the PMB special meeting other than as listed above.

BOC Stock Issuance Proposal: The number of votes cast for the BOC stock issuance proposal must exceed the number of votes cast against the BOC stock issuance proposal.

BOC Adjournment Proposal: The number of votes cast for the BOC adjournment proposal must exceed the number of votes cast against the BOC adjournment proposal.

PMB NEO Compensation Proposal: The PMB NEO compensation proposal requires a vote that satisfies two criteria: (i) the affirmative vote of a majority of the shares represented and voting at a duly held meeting at which a quorum is present, and (ii) the shares voting affirmatively must also constitute at least a majority of the required quorum.

PMB Adjournment Proposal: The PMB adjournment proposal requires a vote that satisfies two criteria: (i) the affirmative vote of a majority of the shares represented and voting at a duly held meeting at which a quorum is present, and (ii) the shares voting affirmatively must also constitute at least a majority of the required quorum.

In addition, each of the directors and certain stockholders of BOC have entered into a voting agreement with PMB in which such director or stockholder has agreed to vote all BOC common stock that he or she owns and has the power to vote in favor of the BOC merger proposal, the BOC stock issuance proposal and any other matter that is required to be approved by the stockholders of BOC to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the merger or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to BOC’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 5,205,334 shares of BOC common stock, allowing them to exercise approximately 10.4% of the voting power of BOC common stock (which does not include shares issuable upon the exercise of stock options or upon the vesting of BOC RSUs that were not outstanding as of the close of business on the record date).

Please follow the instructions set forth on the proxy card or on the voting instruction form provided by the record holder if your BOC stock or PMB shares are held in the name of your bank, broker or other nominee.

You may also cast your vote online during the BOC special meeting or in person at the PMB special meeting.

If your stock or shares are held in “street name,” through a bank, broker or other nominee, that institution will send you separate instructions describing the procedure for voting such shares. “Street name” stockholders or shareholders who wish to vote online during the applicable special meeting will need to obtain a legal proxy form from their bank, broker or other nominee.

Each BOC common stockholder is entitled to one vote for each share of BOC voting common stock owned as of the close of business on the record date, provided that under BOC’s charter, no beneficial owner of more than 10% of the outstanding shares of BOC common stock may vote shares in excess of this limit. As of the close of business on the record date, there were approximately 50,174,678 outstanding shares of BOC common stock entitled to vote. As of that date, approximately 10.9% of such outstanding BOC common stock were beneficially owned by the directors and executive officers of BOC and their affiliates.

The PMB special meeting will be held in the first floor Training Room at PMB’s offices at 949 South Coast Drive, Costa Mesa, California 92626 at 9:00 a.m., local time, on Wednesday, June 23, 2021. We expect to hold the PMB special meeting in person, but we continue to monitor the situation regarding COVID-19 closely. Accordingly, we are planning for the possibility that the PMB special meeting may be subject to special precautions, including limitations on the number of participants in one room or other limitations. In that regard, only PMB shareholders will be admitted to the PMB special meeting. No guests will be permitted. For safety and security purposes, you will need to obtain authorization in advance to attend the PMB special meeting in person. To do so, please make your request by mail to PMB at 949 South Coast Drive, Costa Mesa, CA 92626, Attention: Chief Financial Officer, by email at Curt.Christianssen@pmbank.com or by phone at (714) 438-2500. PMB must receive your request for pre-authorization on or before Tuesday, June 15, 2021.

Brokers who hold shares in “street name” for the beneficial owner of those shares typically have the authority to vote in their discretion on “routine” proposals when they have not received instructions from the beneficial owner. However, brokers are not allowed to exercise their voting discretion with respect to the approval of matters that are “non-routine” without specific instructions from the beneficial owner. All proposals to be voted on at the respective special meetings will be “non-routine” matters.

If you are a BOC common stockholder and you do not instruct your bank, broker or other nominee on how to vote your shares, then your bank, broker or other nominee may not vote your shares on the BOC merger proposal, the BOC stock issuance proposal or the BOC adjournment proposal. The effect of such failure to instruct your bank, broker or nominee differs for each proposal:

If you are a PMB common shareholder and you do not instruct your bank, broker or other nominee on how to vote your shares, then your bank, broker or other nominee may not vote your shares on the PMB merger proposal, the PMB NEO compensation proposal or the PMB adjournment proposal. The effect of such failure to instruct your bank, broker or nominee differs for each proposal:

For purposes of the BOC merger proposal, if a BOC common stockholder responds by proxy with an “abstain” vote or attends the BOC special meeting virtually and abstains from voting, it will have the same effect as a vote cast “AGAINST” the proposal. If a BOC common stockholder does not attend the BOC special meeting virtually and does not respond by proxy, it will also have the same effect as a vote cast “AGAINST” the proposal.

For purposes of the BOC stock issuance proposal and the BOC adjournment proposal, if a BOC common stockholder responds by proxy with an “abstain” vote or attends the BOC special meeting virtually and abstains from voting, it will have no effect on the BOC stock issuance proposal or the BOC adjournment proposal. If a BOC common stockholder does not attend the BOC special meeting virtually and does not respond by proxy, it will also have no effect on the BOC stock issuance proposal or the BOC adjournment proposal.

For the purposes of the PMB merger proposal, if a PMB shareholder responds by proxy with an “abstain” vote or is present in person at the PMB special meeting and abstains from voting, it will have the same effect as a vote cast “AGAINST” the proposal. If a PMB common shareholder is not present at the PMB special meeting and does not respond by proxy, it will also have the same effect as a vote cast “AGAINST” the proposal.

The PMB NEO compensation proposal and the PMB adjournment proposal requires a vote that satisfies two criteria: (i) the affirmative vote of a majority of the shares represented and voting at a duly held meeting at which a quorum is present, and (ii) the shares voting affirmatively must also constitute at least a majority of the required quorum. Accordingly, for purposes of the PMB NEO compensation proposal and the PMB adjournment proposal, abstentions will not affect the outcome under clause (i), which recognizes only actual votes cast. However, abstentions will affect the outcome under clause (ii) if the number of shares voting affirmatively, though a majority of the shares represented and voting, does not constitute a majority of the required quorum.

If you choose any of the first three methods, you must take the described action (or, with respect to the second method, your subsequent proxy card must be received) no later than June 22, 2021, at 5:00 p.m. local time, which is the business day immediately prior to the applicable special meeting. If you choose to send a completed proxy card bearing a later date than your original proxy card or a notice of revocation, the new proxy card or notice of revocation must be received before the beginning of the applicable special meeting.

If you have instructed a bank, broker or other nominee to vote your shares, you must follow the directions you receive from your bank, broker or other nominee in order to change or revoke your vote.

For a more detailed discussion of the material U.S. federal income tax consequences of the transaction, please see the section entitled “Material U.S. Federal Income Tax Consequences of the Merger.”

The tax consequences of the merger to any particular PMB shareholder will depend on that shareholder’s particular facts and circumstances. In addition, a PMB shareholder may be subject to state, local or foreign tax laws that are not discussed in this joint proxy statement/prospectus. Accordingly, if you are a PMB shareholder, you are urged to consult your tax advisor to determine your tax consequences from the merger.

If you are a PMB common shareholder and have any questions about the proxy materials or if you need assistance submitting your proxy or voting your shares or need additional copies of this document or the enclosed proxy card, you should contact PMB Investor Relations at (714) 438-2531.

This summary highlights selected information included in this document and does not contain all of the information that may be important to you. You should read this entire document and its appendices and the other documents to which the parties refer before you decide how to vote with respect to the proposals. In addition, the parties incorporate by reference important business and financial information about PMB and BOC into this document. For a description of this information, please see the section entitled “Incorporation of Certain Documents by Reference.” You may obtain the information incorporated by reference into this document without charge by following the instructions in the section entitled “Where You Can Find More Information” in the forepart of this document. Each item in this summary includes a page reference directing you to a more complete description of that item.

The terms and conditions of the merger are contained in the merger agreement, which is attached to this document as Appendix A. The parties encourage you to read the merger agreement carefully, as it is the legal document that governs the merger.

Under the terms of the merger agreement, PMB will merge with and into BOC, with BOC being the surviving corporation.

In the merger, each PMB common share owned by a PMB shareholder, other than excluded shares, will be converted into the right to receive a number of shares of BOC common stock equal to the exchange ratio. For each fractional share that would otherwise be issued, BOC will pay cash in an amount equal to the fraction of a share of BOC common stock which the holder would otherwise be entitled to receive multiplied by the volume weighted average price of BOC common stock as quoted on the NYSE over the determination period. No interest will be paid or accrue on cash payable to holders in lieu of fractional shares.

After careful consideration, the BOC board of directors recommends that BOC stockholders vote “FOR” the BOC merger proposal, “FOR” the BOC stock issuance proposal and “FOR” the BOC adjournment proposal.

For a more complete description of BOC’s reasons for the merger and the recommendations of the BOC board of directors, please see the sections entitled “The Merger—Recommendation of the BOC Board of Directors and Reasons for the Merger.”

After careful consideration, the PMB board of directors recommends that PMB shareholders vote “FOR” the PMB merger proposal, “FOR” the PMB NEO compensation proposal and “FOR” the PMB adjournment proposal.

For a more complete description of PMB’s reasons for the merger and the recommendations of the PMB board of directors, please see the section entitled “The Merger—Recommendation of the PMB Board of Directors and Reasons for the Merger.”

In connection with the merger, BOC’s financial advisor, Piper Sandler & Co., which we refer to as Piper Sandler, delivered a written opinion, dated March 19, 2021, to the BOC board of directors to the effect that, as of the date thereof and subject to the procedures followed, assumptions made, matters considered and the qualifications and limitations on the review undertaken by Piper Sandler as set forth therein, the merger consideration was fair, from a financial point of view, to BOC. Piper Sandler’s opinion was directed to the BOC board of directors in connection with its consideration of the merger agreement and the merger and does not constitute a recommendation to any BOC stockholder as to how any such stockholder should vote at any meeting of stockholders called to consider and vote upon the BOC merger proposal or the BOC stock issuance proposal. Piper Sandler’s opinion speaks only as of the date thereof. The full text of Piper Sandler’s opinion is attached

as Appendix E to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by Piper Sandler in rendering its opinion. Piper Sandler’s opinion was directed only to the fairness, from a financial point of view, of the merger consideration to BOC and did not address the underlying business decision of BOC to engage in the merger, the form or structure of the merger or any other transactions contemplated in the merger agreement, the relative merits of the merger as compared to any alternative transactions or business strategies that might exist for BOC or the effect of any other transaction in which BOC might engage.

In connection with the merger, PMB’s financial advisor, Keefe, Bruyette & Woods, Inc., which we refer to as KBW, delivered a written opinion, dated March 22, 2021, to the PMB board of directors as to the fairness, from a financial point of view and as of the date of the opinion, to the holders of PMB common shares of the exchange ratio in the proposed merger. The full text of the opinion, which describes the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW in preparing the opinion, is attached as Appendix D to this document. The opinion was for the information of, and was directed to, the PMB board of directors in connection with its consideration of the financial terms of the merger. The opinion does not address the underlying business decision of PMB to engage in the merger or enter into the merger agreement or constitute a recommendation to the PMB board of directors in connection with the merger, and it does not constitute a recommendation to any holder of PMB common stock or any shareholder or stockholder of any other entity as to how to vote or act in connection with the merger or any other matter.

The BOC special meeting will be held virtually at http://www.virtualshareholdermeeting.com/BANC2021SM at 8:00 a.m., local time, on Wednesday, June 23, 2021. At the BOC special meeting, holders of BOC common stock will be asked to approve the BOC merger proposal, the BOC stock issuance proposal and the BOC adjournment proposal.

The BOC board of directors has fixed the close of business on Monday, May 10, 2021 as the record date for determining the holders of BOC common stock entitled to receive notice of and to vote at the BOC special meeting. As of the close of business on the record date, there were 50,174,678 shares of BOC common stock outstanding and entitled to vote at the BOC special meeting held by 1,274 stockholders of record. Each share of BOC voting common stock entitles the holder to one vote on each proposal to be considered at the BOC special meeting, provided that under BOC’s charter, no beneficial owner of more than 10% of the outstanding shares of BOC common stock may vote shares in excess of this limit.

As of the close of business on the record date, directors and executive officers of BOC and their affiliates owned and were entitled to vote 5,460,783 shares of BOC common stock, representing approximately 10.9% of the BOC common stock outstanding on that date. As of the close of business on the record date, PMB beneficially held no BOC common stock.

Each of the directors and certain stockholders of BOC have entered into a voting agreement with PMB in which such director or stockholder has agreed to vote all BOC common stock that he or she owns and has the power to vote in favor of the BOC merger proposal, the BOC stock issuance proposal and any other matter that is required to be approved by the stockholders of BOC to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the merger or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to BOC’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 5,205,334 shares of BOC common stock, allowing them to exercise approximately 10.4% of the voting power of BOC common stock (which does not include shares issuable upon the exercise of stock options or upon the vesting of BOC RSUs that were not outstanding as of the close of business on the record date).

Approval of the BOC merger proposal requires the affirmative vote of a majority of the outstanding shares of BOC common stock entitled to vote on the BOC merger proposal. Approval of the BOC stock issuance proposal and the BOC adjournment proposal requires the number of votes cast for the proposal to exceed the number of votes cast against the proposal.

The PMB special meeting will be held in the first floor Training Room at PMB’s offices at 949 South Coast Drive, Costa Mesa, California 92626 at 9:00 a.m., local time, on Wednesday, June 23, 2021. At the PMB special meeting, holders of PMB common shares will be asked to approve the PMB merger proposal, the PMB NEO compensation proposal and the PMB adjournment proposal.

The PMB board of directors has fixed the close of business on Monday, May 10, 2021 as the record date for determining the holders of PMB common shares entitled to receive notice of and to vote at the PMB special meeting. As of the close of business on the record date, there were 22,322,184 PMB common shares outstanding and entitled to vote at the PMB special meeting held by 84 shareholders of record. Each PMB voting common share entitles the holder to one vote on each proposal to be considered at the PMB special meeting.

As of the close of business on the record date, directors and executive officers of PMB and their affiliates owned and were entitled to vote 3,166,347 PMB common shares, representing approximately 14.2% of the PMB common shares outstanding on that date. As of the close of business on the record date, BOC beneficially held no PMB common shares.

Each of the directors and certain shareholders of PMB have entered into a voting agreement with BOC in which such director or shareholder has agreed to vote all PMB common shares that he or she owns and has the power to vote in favor of the PMB merger proposal and any other matter that is required to be approved by the shareholders of PMB to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the principal terms of the merger agreement or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to PMB’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 2,754,062 PMB common shares, allowing them to exercise approximately 12.3% of the voting power of PMB common shares (which does not include shares issuable upon the exercise of stock options or upon the vesting of PMB RSUs that were not outstanding as of the close of business on the record date).

Approval of the PMB merger proposal requires the affirmative vote of a majority of the outstanding shares entitled to vote on such proposal. Approval of the PMB NEO compensation proposal and the PMB adjournment proposal requires a vote that satisfies two criteria: (i) the affirmative vote of a majority of the shares represented and voting at a duly held meeting at which a quorum is present, and (ii) the shares voting affirmatively must also constitute at least a majority of the required quorum.

In considering the recommendations of the PMB board of directors, PMB shareholders should be aware that certain directors and executive officers of PMB have interests in the merger that may differ from, or be in addition to, the interests of PMB shareholders generally. The PMB board of directors was aware of these interests and considered them, among other matters, when it approved the merger and in making its recommendation that the PMB shareholders approve the principal terms of the merger agreement. These interests include:

For a more complete description of the interests of PMB’s directors and executive officers in the merger, see “The Mergers—Interests of PMB Directors and Executive Officers in the Merger.”

At the effective time of the merger, each PMB stock option that is outstanding immediately prior to the effective time, whether vested or unvested, will be cancelled and will entitle the holder thereof to receive an amount in cash equal to the product of (i) the total number of PMB common shares subject to such option and (ii) the excess, if any, of (A) an amount equal to the product of the BOC average closing price and 0.50 over (B) the exercise price per PMB common share underlying such option, less any applicable taxes required to be withheld with respect to such payment. Any PMB stock options which have an exercise price per share that is greater than or equal to the product of the BOC average closing price and 0.50 will be cancelled at the effective time of the merger for no consideration or payment.

At the effective time of the merger, each PMB restricted share and each PMB RSU will, automatically and without any action on the part of the holder of such PMB restricted shares or PMB RSUs, accelerate in full, be cancelled and will only entitle the holder of such PMB restricted shares or PMB RSUs to receive, on the first regular payroll date following the closing date of the merger, an amount in cash equal to the product of (i) such holder’s total number of PMB restricted shares or RSUs, as applicable, and (ii) an amount equal to the product of the BOC average closing price and 0.50, less any applicable taxes required to be withheld with respect to such vesting, which tax withholding may, at the election of the holder, be effected by deduction from such cash amount equal to the amount of taxes to be withheld.

The directors and officers of BOC immediately prior to the effective time, together with two directors from the PMB board prior to the effective time selected by the BOC CNG Committee, will be the directors and officers of the surviving corporation after the consummation of the merger, and will serve until such time as their successors are duly elected and qualified. BOC has agreed that it will, through the BOC board and subject to its fiduciary duties to its stockholders, take all necessary action to nominate such PMB directors for election to the BOC board in the proxy statement relating to the first annual meeting of stockholders of BOC following the effective time.

BOC and PMB have each agreed to use reasonable best efforts to obtain all regulatory approvals required to complete the merger and the bank merger and the other transactions contemplated by the merger agreement. Regulatory approvals are required from the Federal Reserve Board, referred to as the FRB, and the Office of the Comptroller of Currency, referred to as the OCC. As of the date of this joint proxy statement/prospectus, BOC and PMB have not submitted applications and notifications to obtain the required regulatory approvals. There can be no assurances that such approvals will be received on a timely basis, or as to the ability of BOC or PMB to obtain the approvals on satisfactory terms or the absence of litigation challenging such approvals. The regulatory approvals to which completion of the merger and bank merger are subject are described in more detail under the section entitled “The Merger—Regulatory Approvals Required for the Merger.”

The respective obligation of each party to effect the merger is subject to the satisfaction or written waiver at or prior to the effective time of each of the following conditions:

PMB’s obligation to effect the merger is also subject to the fulfillment or waiver of the following conditions:

BOC’s obligation to complete the merger is also subject to the satisfaction or waiver of the following conditions:

For more information, please see the section entitled “The Merger Agreement—Conditions to Consummation of the Merger.”

Under the terms of the merger agreement, PMB has agreed not to, directly or indirectly:

However, the above restriction would not prevent PMB or its board of directors from:

only if, however, in the cases referred to in the second and third bullet points above, the PMB board of directors determines in good faith (after consultation with outside legal counsel) that the failure to take such action would reasonably be expected to violate the directors’ fiduciary duties under applicable law.

Further, the merger agreement provides that, subject to certain exceptions, the PMB board of directors and each committee thereof will not:

For more information, please see the section entitled “The Merger Agreement—Acquisition Proposals.”

The merger agreement may be terminated and the merger may be abandoned:

For more information, please see the section entitled “The Merger Agreement—Termination of the Merger Agreement.”

PMB must pay BOC a termination fee of $8,500,000 in the following circumstances:

For more information, please see the section entitled “The Merger Agreement—Termination Fee.”

Each of the directors and certain shareholders of PMB have entered into a voting agreement with BOC in which such director or shareholder has agreed to vote all PMB common shares that he or she owns and has the power to vote in favor of the PMB merger proposal and any other matter that is required to be approved by the shareholders of PMB to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the principal terms of the merger agreement or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to PMB’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 2,754,062 PMB common shares, allowing them to exercise approximately 12.3% of the voting power of PMB common shares (which does not include shares issuable upon the exercise of stock options or upon the vesting of PMB RSUs that were not outstanding as of the close of business on the record date).

Each of the directors and certain stockholders of BOC have entered into a voting agreement with PMB in which such director or stockholder has agreed to vote all BOC common stock that he or she owns and has the power to vote in favor of the BOC merger proposal, the BOC stock issuance proposal and any other matter that is required to be approved by the stockholders of BOC to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the merger or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to BOC’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 5,205,334 shares of BOC common stock, allowing them to exercise approximately 10.4% of the voting power of BOC common stock (which does not include shares issuable upon the exercise of stock options or upon the vesting of BOC RSUs that were not outstanding as of the close of business on the record date).

The voting agreements terminate in certain circumstances, including in the event that the merger agreement is terminated in accordance with its terms.

For more information, please see the section entitled “The Merger Agreement—Voting Agreements.”

The merger is intended to qualify as a tax-deferred reorganization within the meaning of Section 368(a) of the Code. Assuming the merger qualifies as a reorganization, PMB common shareholders generally will not recognize any gain or loss for U.S. federal income tax purposes on the exchange of their PMB common shares for BOC common stock in the merger, except for any gain or loss that may result from the receipt of cash instead of a fractional share of BOC common stock. It is a condition to the completion of the merger that BOC and PMB receive written opinions from their respective counsel to the effect that the merger will qualify as a reorganization within the meaning of Section 368(a) of the Code.

Tax matters are complicated and the tax consequences of the merger to each PMB shareholder may depend on such shareholder’s particular facts and circumstances. PMB shareholders are urged to consult their tax advisors to understand fully the tax consequences to them of the merger. For more information, please see the section entitled “Material U.S. Federal Income Tax Consequences of the Merger.”

The rights of PMB shareholders who continue as BOC stockholders after the merger will be governed by the charter and bylaws of BOC and Maryland law rather than by the articles of incorporation and bylaws of PMB and California law. For more information, please see the section entitled “Comparison of Shareholders’ Rights.”

Banc of California, Inc.

Banc of California, Inc., a Maryland corporation, is a bank holding company registered under the Bank Holding Company Act of 1956, as amended, referred to as the BHC Act, with corporate headquarters in Santa Ana, California. BOC’s principal business is to serve as the holding company for BOC’s wholly owned subsidiary, Banc of California, National Association. References to BOC refer to BOC together with BOC Bank and its other subsidiaries on a consolidated basis.

BOC is a relationship-focused business bank that delivers comprehensive products and solutions for businesses, business owners and individuals. It offers a full array of competitively priced and client-tailored loan and deposit products and services through 29 full service branches extending from San Diego to Santa Barbara. It also offers commercial loan products, including commercial and industrial loans, commercial real estate loans and multifamily loans, SBA loans, construction loans and other consumer loans. In addition, BOC has a single family residential, or SFR, mortgage loan portfolio that it services.

As of March 31, 2021, on a consolidated basis, BOC had total assets of $7.9 billion, total loans of $5.8 billion, total deposits of $6.1 billion, and stockholders’ equity of $804.7 million.

Pacific Mercantile Bancorp

Pacific Mercantile Bancorp is the parent holding company of Pacific Mercantile Bank, which opened for business March 1, 1999. PM Bank, which is an FDIC insured, California state-chartered bank and a member of the Federal Reserve System, provides a wide range of commercial banking services to businesses, business professionals and individual clients. PM Bank is headquartered in Orange County and operates a total of seven offices in Southern California, located in Orange, Los Angeles, San Diego, and San Bernardino counties. PM Bank offers tailored flexible solutions for its clients including an array of loan and deposit products, sophisticated cash management services, and comprehensive online banking services.

PM Bank’s commercial lending solutions include working capital lines of credit and asset based lending, 7(a) and 504 Small Business Administration loans, commercial real estate loans, growth capital loans, equipment financing, letters of credit and corporate credit cards. PM Bank’s depository and corporate banking services include cash and treasury management solutions, interest-bearing term deposit accounts, checking accounts,

automated clearinghouse payment and wire solutions, fraud protection, remote deposit capture, courier services and online banking. PM Bank serves clients operating in a global marketplace through services including letters of credit and import/export financing. PMB has developed its Horizon Analytics tool which provides financial modeling and analysis to help its customers succeed.

As of March 31, 2021, on a consolidated basis, PMB had total assets of $1.6 billion, total loans of $1.2 billion, total deposits of $1.4 billion and total shareholders’ equity of $161.3 million.

Before voting at the applicable special meeting, you should carefully consider all of the information contained in or incorporated by reference into this document, including the risk factors set forth in the section entitled “Risk Factors” or described in BOC’s and PMB’s respective Annual Reports on Form 10-K for the year ended on December 31, 2020 and other reports filed with the SEC, which are incorporated by reference into this document. Please see “Where You Can Find More Information” and “Incorporation of Certain Documents by Reference.”

PMB, PMB’s board of directors and BOC are parties to three claims and litigation related to the merger. All three of these claims have been filed by purported shareholders of PMB, each of whom seeks to enjoin the merger and other relief. The complaints assert claims against PMB, the members of PMB’s board of directors, and in one case, BOC, under Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder by filing this joint proxy statement/prospectus that allegedly contains false statements and omits material information. One complaint also asserts claims under Section 20(a) of the Exchange Act against BOC and PMB’s board of directors due to their positions as controlling persons over the parties that allegedly knowingly violated Section 14(a).

The following table presents basic and diluted per common share data, cash dividends and book value for BOC and PMB on a historical basis, pro forma combined consolidated basis, and the combined entity on a pro forma equivalent basis. The pro forma basic and diluted earnings per share information was computed as if the merger had been completed on January 1, 2020. The pro forma book value per share information was computed as if the merger had been completed on March 31, 2021.

The following pro forma information has been derived from and should be read in conjunction with the audited consolidated financial statements for the quarter ended March 31, 2021 and the year ended December 31, 2020 for BOC and PMB, each of which are incorporated by reference in this joint proxy statement/prospectus. This information is presented for illustrative purposes only and you should not rely on the pro forma combined or pro forma equivalent amounts as they are not necessarily indicative of the consolidated operating results or consolidated financial position that would have occurred if the merger had been completed as of the dates indicated, nor are they necessarily indicative of the future consolidated operating results or consolidated financial position of the combined company.

Upon completion of the merger, each PMB common share (other than excluded shares) will be converted into the right to receive merger consideration consisting of the number of shares of BOC common stock equal to the exchange ratio, pursuant to the terms of the merger agreement. The number of shares of BOC common stock to be received by a PMB shareholder will be determined based on a fixed exchange ratio of 0.50 of a share of BOC common stock for each PMB common share (other than excluded shares). Accordingly, the value of the merger consideration to be received by PMB shareholders will be based on the value of BOC common stock at closing. The value of the BOC common stock to be received by PMB shareholders in the merger may vary from the value as of the date the merger was announced, the date that this document was mailed to PMB shareholders and the date of the PMB special meeting. Any change in the market price of BOC common stock prior to completion of the merger will affect the value of the merger consideration that PMB shareholders will receive upon completion of the merger. Accordingly, at the time of the PMB special meeting, PMB shareholders will not know or be able to calculate the value of the per share consideration they would receive upon completion of the merger. Share price changes may result from a variety of factors, including general market and economic conditions, changes in BOC’s or PMB’s businesses, operations and prospects, and regulatory considerations, among other things. Many of these factors are beyond the control of BOC and PMB. PMB shareholders should obtain current market quotations for BOC common stock before voting their shares at the PMB special meeting.

BOC stockholders currently have the right to vote in the election of the BOC board of directors and on other matters affecting BOC. PMB shareholders currently have the right to vote in the election of the PMB board of directors and on other matters affecting PMB. Upon the completion of the merger, except for shareholders who own common shares in both BOC and PMB, BOC stockholders and PMB shareholders will be stockholders of BOC with a percentage ownership of BOC that is smaller than their current percentage ownership of BOC or PMB, as applicable. It is currently expected that former shareholders of PMB as a group will receive shares in the merger constituting approximately 19% of the outstanding shares of BOC’s common stock immediately after the merger. Because of this, both BOC stockholders and PMB shareholders will have less influence on the management and policies of BOC than they now have on the management and policies of BOC or PMB, as applicable.

Shares of BOC common stock that are issued to PMB shareholders in the merger will be freely tradable without restrictions or further registration under the Securities Act. As of the close of business on the record date, BOC had approximately 50,174,678 shares of common stock outstanding and 3,192,230 shares of BOC common stock were reserved for issuance under BOC’s equity incentive plans. Based on the PMB common shares currently outstanding, BOC currently expects to issue approximately 11,893,692 shares of its common stock in connection with the merger.

Because of the significantly enhanced liquidity of BOC common stock as compared to PMB common shares due to the greater public float and trading volume of BOC common stock relative to PMB common shares, if the merger is completed, PMB’s former shareholders may sell substantial amounts of BOC common stock in the public market following completion of the merger. Any such sales may cause the market price of BOC common stock to decrease. These sales might also make it more difficult for BOC to sell equity or equity-related securities at a time and price that it otherwise would deem appropriate.

The success of the merger will depend on, among other things, BOC’s ability to combine and integrate the business of PMB into BOC’s business. If BOC is not able to successfully achieve this objective, the anticipated benefits of the merger may not be realized fully, or at all, or may take longer to realize than expected.

BOC and PMB have operated and, until the consummation of the merger, will continue to operate independently. It is possible that the integration process or other factors could result in the loss or departure of key employees, the disruption of the ongoing business of BOC or PMB or inconsistencies in standards, controls, procedures and policies. It is also possible that clients, customers, depositors and counterparties of PMB could choose to discontinue their relationships with BOC post-merger because they prefer doing business with a different financial institution, which would adversely affect the future anticipated performance of BOC. These transition matters could have an adverse effect on BOC and PMB during the pre-merger period and the combined company for an undetermined amount of time after the consummation of the merger.

Before the transactions contemplated by the merger agreement, including the merger and the bank merger, may be completed, various approvals must be obtained from bank regulatory authorities. These governmental entities may impose conditions on the granting of such approvals. Such conditions or changes and the process of obtaining regulatory approvals could have the effect of delaying completion of the merger or of imposing additional costs or limitations on BOC following the merger. The regulatory approvals may not be received in a timely fashion, may contain conditions on the completion of the merger that are not anticipated or cannot be met, or may not be received at all. If the consummation of the merger is delayed, including by a delay in receipt of necessary governmental approvals, the business, financial condition and results of operations of each company may also be materially adversely affected.

The merger agreement is subject to a number of conditions which must be fulfilled in order to complete the merger. Those conditions include: (i) approval of the principal terms of the merger agreement by PMB shareholders, (ii) approval of the merger and the issuance of BOC common stock in connection with the merger by BOC stockholders, (iii) absence of any governmental order or law prohibiting completion of the merger, and (iv) effectiveness of the registration statement of which this document is a part.

The obligation of each party to consummate the merger is also conditioned upon (i) subject to certain exceptions, the accuracy of the representations and warranties of the other party, (ii) performance in all material respects by the other party of its obligations under the merger agreement, (iii) receipt by such party of a tax opinion to the effect that the merger will qualify as a reorganization within the meaning of Section 368(a) of the Code, and (iv) the absence of a material adverse effect with respect to the other party since the date of the merger agreement. The obligation of BOC to consummate the merger is also conditioned upon (i) the sum of the adjusted shareholders’ equity and allowance for loan losses of PMB being outside of specified levels and (ii) the receipt of certain required regulatory approvals and such approvals not containing materially burdensome regulatory conditions. The obligation of PMB to consummate the merger is also conditioned upon the receipt of certain required regulatory approvals.

These conditions to the consummation of the merger may not be fulfilled and, accordingly, the merger may not be completed. In addition, if the merger is not completed by the end date, either BOC or PMB may choose not to proceed with the merger, and the parties can mutually decide to terminate the merger agreement at any time, before or after the PMB shareholder approval or the BOC stockholder approval.

Furthermore, prior to the PMB shareholder approval, BOC may terminate the merger agreement and require payment of an $8.5 million termination fee if PMB materially breaches the restriction against soliciting alternative acquisition proposals, if PMB’s board of directors recommends against the merger, if PMB’s board of directors fails to reaffirm its recommendation in response to an alternative acquisition proposal after receiving a written request to do so from BOC, or if PMB’s board of directors recommends that PMB shareholders tender (or fails to recommend against tendering) their shares in a competing tender offer. PMB must also pay the

$8.5 million termination fee if (i) an alternative acquisition proposal has been made or announced, (ii) the merger agreement is terminated because (x) the merger was not consummated by the end date or (y) either the PMB shareholder approval has not been obtained or the BOC stockholder approval has not been obtained at the respective special meetings, and in the case of each of clauses (x) and (y), the PMB shareholder approval has not been obtained, and (iii) within 12 months after the termination of the merger agreement, PMB enters into a definitive agreement with respect to or consummates a proposal by a third party to acquire 50% or more of the assets or voting power of PMB.

If the merger is not consummated, the ongoing business, financial condition and results of operations of each party may be materially adversely affected and the market price of each party’s common stock may decline significantly, particularly to the extent that the current market price reflects a market assumption that the merger will be consummated. If the consummation of the merger is delayed, including by the receipt of a competing acquisition proposal, the business, financial condition and results of operations of each company may be materially adversely affected.

In addition, each party has incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement. If the merger is not completed, the parties would have to recognize these expenses, including, in the case of PMB under certain circumstances, a termination fee, without realizing the expected benefits of the transaction. Any of the foregoing, or other risks arising in connection with the failure of or delay in consummating the merger, including the diversion of management attention from pursuing other opportunities and the constraints in the merger agreement on each party’s ongoing business during the pendency of the merger, could have a material adverse effect on each party’s business, financial condition and results of operations.

If the merger agreement is terminated and a party’s board of directors seeks another merger or business combination, such party’s shareholders cannot be certain that such party will be able to find a party willing to engage in a transaction on more attractive terms than the merger.

Uncertainty about the effect of the merger on employees, customers, suppliers and vendors may have an adverse effect on the business, financial condition and results of operations of PMB and, consequently, BOC. These uncertainties and contemplated changes may impair PMB’s ability to attract, retain and motivate key personnel and customers pending the consummation of the merger, as such personnel and customers may experience uncertainty about their future roles following the consummation of the merger. Additionally, these uncertainties and contemplated changes could cause customers, suppliers, vendors and others who deal with PMB to seek to change existing business relationships with PMB or fail to extend an existing relationship with PMB. In addition, competitors may target PMB’s existing customers by highlighting potential uncertainties and integration difficulties that may result from the merger.

PMB has a small number of key personnel. The pursuit of the merger and the preparation for the integration may place a burden on PMB’s management and internal resources. Any significant diversion of management attention away from ongoing business concerns and any difficulties encountered in the transition and integration process could have a material adverse effect on PMB’s business, financial condition and results of operations.

In addition, the merger agreement restricts PMB and BOC from taking certain actions without the other party’s consent while the merger is pending. These restrictions may, among other matters, and subject to certain exceptions, prevent PMB from pursuing otherwise attractive business opportunities, selling assets, incurring indebtedness, engaging in significant capital expenditures, entering into other transactions or making other changes to PMB’s business prior to consummation of the merger or termination of the merger agreement. These restrictions could have a material adverse effect on PMB’s business, financial condition and results of operations. Please see the section entitled “The Merger Agreement—Conduct of Business Prior to the Completion of the Merger” for a description of the restrictive covenants applicable to PMB and BOC.

In considering the recommendations of the PMB board of directors, PMB shareholders should be aware that certain directors and executive officers of PMB have interests in the merger that may differ from, or be in

addition to, the interests of PMB shareholders generally. The PMB board of directors was aware of these interests and considered them, among other matters, when it approved the merger and in making its recommendation that the PMB shareholders approve the principal terms of the merger agreement. These interests include:

For a more complete description of the interests of PMB’s directors and executive officers in the merger, see “The Mergers—Interests of PMB Directors and Executive Officers in the Merger.”

Upon completion of the merger, the rights of former PMB shareholders will be governed by the charter and bylaws of BOC. The rights associated with PMB common shares are different from the rights associated with BOC common stock. In addition, the rights of stockholders under Maryland law, where BOC is incorporated, may differ from the rights of shareholders under California law, where PMB is incorporated. Please see the section entitled “Comparison of Shareholders’ Rights” for a discussion of the different rights associated with BOC common stock.

The merger agreement contains provisions that may discourage a third party from submitting a business combination proposal to PMB that might result in greater value to PMB shareholders than the merger. These provisions include a general prohibition on PMB soliciting, or, subject to certain exceptions, entering into discussions with any third party regarding any acquisition proposal or offers for competing transactions. In addition, in some circumstances upon termination of the merger agreement, PMB may be required to pay BOC an $8.5 million termination fee. However, the failure of PMB shareholders to approve the merger agreement will not in and of itself trigger PMB’s obligation to pay a termination fee, unless other factors also exist, including a third-party proposal to acquire PMB and entry into a definitive agreement with respect to an acquisition of PMB, or consummation of an acquisition of PMB, in each case within 12 months following termination.

Each of the directors and certain shareholders of PMB have entered into a voting agreement with BOC in which such director or shareholder has agreed to vote all PMB common shares that he or she owns and has the power to vote in favor of the PMB merger proposal and any other matter that is required to be approved by the shareholders of PMB to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the principal terms of the merger agreement or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to PMB’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 2,754,062 PMB common shares, allowing them to exercise approximately 12.3% of the voting power of PMB common shares (which does not include shares issuable upon the exercise of stock options or upon the vesting of PMB RSUs that were not outstanding as of the close of business on the record date). For more information, please see the section entitled “The Merger Agreement—Voting Agreements.” PMB also has an unqualified obligation to submit the PMB merger proposal to a vote of PMB shareholders, even if PMB receives a proposal that its board of directors believes is superior to the merger.

BOC’s charter provides for, among other things, the issuance of preferred stock without further stockholder approval, super majority stockholder approval of certain business transactions, restrictions on voting of BOC equity securities above certain ownership levels and consideration of non-monetary factors in evaluating a takeover offer. Although these provisions were not adopted for the express purpose of preventing or impeding a takeover of BOC without the approval of the BOC board of directors, such provisions may have that effect. Such provisions may prevent former PMB shareholders who receive shares of BOC common stock in the merger from taking part in a transaction in which such shareholders could realize a premium over the current market price of BOC common stock. See “Comparison of Shareholders’ Rights” for a discussion of the different rights associated with BOC common stock.

BOC expects to incur substantial expenses in connection with consummation of the merger and integrating the business, operations, networks, systems, technologies, policies and procedures of PMB into that of BOC. Although BOC and PMB have assumed that a certain level of transaction and combination expenses would be incurred, there are a number of factors beyond their control that could affect the total amount or the timing of their combination expenses. Many of the expenses that will be incurred, by their nature, are difficult to estimate accurately at the present time. As a result of these expenses, both BOC and PMB expect to take charges against their earnings before completion of the merger and BOC expects to take charges against its earnings after completion of the merger. The charges taken in connection with the merger are expected to be significant, although the aggregate amount and timing of such charges are uncertain at present.

BOC’s board of directors received an opinion from BOC’s financial advisor on March 19, 2021 and PMB’s board of directors received an opinion from PMB’s financial advisor on March 22, 2021 regarding the fairness, from a financial point of view and as of that date, of the merger consideration to BOC (in the case of BOC’s financial advisor) and the fairness, from a financial point of view and as of that date, of the exchange ratio to the holders of PMB common stock (in the case of PMB’s financial advisor). Changes in the operations and prospects of BOC or PMB, general market and economic conditions and other factors which may be beyond the control of BOC or PMB may have altered the value of BOC or PMB or the market prices of shares of BOC or PMB common stock as of the date of this document, or may alter such values and market prices by the time the merger is completed. The opinions did not speak as of the time the merger is completed or as of any date other than the date of the applicable opinion. However, PMB’s board of directors’ recommendation that PMB shareholders vote “FOR” the PMB merger proposal is made as of the date of this document, and BOC’s board of directors’ recommendation that BOC stockholders vote “FOR” the BOC merger proposal and the BOC stock issuance proposal is made as of the date of this document. For a description of the opinions of BOC’s and PMB’s respective financial advisors, see “The Mergers—Opinion of BOC’s Financial Advisor” and “The Mergers—Opinion of PMB’s Financial Advisor” included elsewhere in this joint proxy statement/prospectus.

The unaudited pro forma combined condensed consolidated financial information in this document is presented for illustrative purposes only and is not necessarily indicative of what BOC’s actual financial condition or results of operations would have been had the merger been completed on the dates indicated. The pro forma condensed combined financial information reflects adjustments, which are based upon preliminary estimates, to record the PMB identifiable tangible and intangible assets acquired and liabilities assumed at fair value and the resulting goodwill recognized. The purchase price allocation reflected in this document is preliminary and final allocation of the purchase price and goodwill recognized will be based upon the actual purchase price and the estimated fair value of the assets acquired and liabilities assumed of PMB as of the date of the completion of the merger. Accordingly, the final acquisition accounting adjustments may differ materially from the pro forma adjustments reflected in this document. For more information, please see the section entitled “Unaudited Pro Forma Combined Condensed Consolidated Financial Information” beginning on page 103.

BOC is, and will continue to be, subject to the risks described in BOC’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020, as updated by subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, all of which are filed with the SEC and incorporated by reference into this joint proxy statement/prospectus. See “Documents Incorporated by Reference” and “Where You Can Find More Information” included elsewhere in this joint proxy statement/prospectus.

PMB is, and will continue to be, subject to the risks described in PMB’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020, as updated by subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, all of which are filed with the SEC and incorporated by reference into this joint proxy statement/prospectus. See “Documents Incorporated by Reference” and “Where You Can Find More Information” included elsewhere in this joint proxy statement/prospectus.

This joint proxy statement/prospectus contains certain forward-looking information about BOC, PMB, and the combined company after the close of the merger and the bank merger that is intended to be covered by the safe harbor for “forward-looking statements” provided by the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact are forward-looking statements. Such statements involve inherent risks, uncertainties and contingencies, many of which are difficult to predict and are generally beyond the control of BOC, PMB and the combined company. Readers are cautioned that a number of important factors could cause actual results to differ materially from those expressed in, or implied or projected by, such forward-looking statements. In addition to factors previously disclosed in reports filed by BOC and PMB with the SEC, risks and uncertainties for each institution and the combined institution include, but are not limited to:

All forward-looking statements included in this joint proxy statement/prospectus are based on information available at the time of the joint proxy statement/prospectus. Pro forma, projected and estimated numbers are used for illustrative purposes only and are not forecasts, and actual results may differ materially.

BOC and PMB are under no obligation to (and expressly disclaim any such obligation to) update or alter these forward-looking statements, whether as a result of new information, future events or otherwise except as required by law.

The BOC special meeting will be held virtually at http://www.virtualshareholdermeeting.com/BANC2021SM, on Wednesday, June 23, 2021, at 8:00 a.m., local time. On or about Friday, May 14, 2021, BOC commenced mailing of this joint proxy statement/prospectus and the enclosed form of proxy to its stockholders entitled to vote at the BOC special meeting. Holders of record of BOC voting common stock can vote their shares electronically by the Internet and submit questions online during the BOC special meeting by logging in to the website listed above using the 16-digit control number included in their proxy card.

At the BOC special meeting, BOC common stockholders will be asked to consider and vote upon the following proposals:

BOC will transact no other business at the BOC special meeting other than as listed above.

After careful consideration, the BOC board of directors has approved the merger and the issuance of BOC common stock in connection with the merger, and determined that the merger and the issuance of BOC common stock in connection with the merger are advisable and fair to and in the best interests of BOC and its stockholders.

The BOC board of directors recommends that you vote “FOR” the merger proposal, “FOR” the BOC stock issuance proposal and “FOR” the BOC adjournment proposal. Please see the section entitled “The Merger—Recommendation of the BOC Board of Directors and Reasons for the Merger.”

The BOC board of directors has fixed the close of business on Monday, May 10, 2021 as the record date for determining the holders of BOC common stock entitled to receive notice of and to vote at the BOC special meeting.

As of the close of business on the record date, there were 50,174,678 shares of BOC common stock outstanding and entitled to vote at the BOC special meeting held by 1,274 shareholders of record. Each share of BOC voting common stock entitles the holder to one vote on each proposal to be considered at the BOC special meeting; provided, however, that under Section F of Article 6 of BOC’s charter, no stockholder who beneficially owns more than 10% of the shares of BOC common stock outstanding as of the record date may vote shares held in excess of this limit.

One-third of the stock entitled to vote, represented in person or by proxy, constitutes a quorum for transacting business at the BOC special meeting. Abstentions will be counted as represented at the BOC special meeting for purposes of determining the presence or absence of a quorum for all matters voted on at the BOC special meeting.

Since none of the proposals to be voted on at the BOC special meeting are routine matters for which brokers may have discretionary authority to vote, there can be no broker non-votes at the BOC special meeting. Consequently, failure to provide instructions to your bank, broker or other nominee on how to vote will result in your shares not being counted as represented for purposes of establishing a quorum at the BOC special meeting. Please see “—Shares Held in ‘Street Name”’ below for further information.

As of the close of business on the record date, directors and executive officers of BOC and their affiliates owned and were entitled to vote 5,460,783 shares of BOC common stock, representing approximately 10.9% of the BOC common stock outstanding on that date. As of the close of business on the record date, PMB beneficially held no BOC common stock.

In connection with the merger agreement, each of the directors and certain stockholders of BOC have entered into a voting agreement with PMB in which such director or stockholder has agreed to vote all BOC common stock that he or she owns and has the power to vote in favor of the BOC merger proposal, the BOC stock issuance proposal and any other matter that is required to be approved by the stockholders of BOC to facilitate the transactions contemplated by the merger agreement. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 5,205,334 shares of BOC common stock, allowing them to exercise approximately 10.4% of the voting power of BOC common stock (which does not include shares issuable upon the exercise of stock options or upon the vesting of BOC RSUs that were not outstanding as of the close of business on the record date).

Approval of each of the proposals to be voted on at the BOC special meeting by the BOC common stockholders will require the following votes:

For purposes of the BOC special meeting, an abstention occurs when a BOC common stockholder is present at the BOC special meeting, either virtually or represented by proxy, but abstains from voting.

Abstentions will be counted as represented at the BOC special meeting for purposes of determining the presence or absence of a quorum for all matters voted on at the BOC special meeting.

For purposes of the BOC merger proposal, if a BOC common stockholder responds by proxy with an “abstain” vote or attends the BOC special meeting virtually and abstains from voting, it will have the same effect as a vote cast “AGAINST” the proposal. If a BOC common stockholder does not attend the BOC special meeting virtually and does not respond by proxy, it will also have the same effect as a vote cast “AGAINST” the proposal.

For purposes of the BOC stock issuance proposal and the BOC adjournment proposal, if a BOC common stockholder responds by proxy with an “abstain” vote or is attends the BOC special meeting virtually and abstains from voting, it will have no effect on the BOC stock issuance proposal or the BOC adjournment proposal. If a BOC common stockholder does not attend the BOC special meeting virtually and does not respond by proxy, it will also have no effect on the BOC stock issuance proposal or the BOC adjournment proposal.

Giving a proxy means that a stockholder authorizes the persons named in the proxy to vote such holder’s shares at the BOC special meeting in the manner such holder directs. A BOC common stockholder may vote by proxy or may vote online during the BOC special meeting.

The method of voting by proxy differs for shares held by stockholders of record and shares held in “street name.”

If your shares of BOC common stock are registered directly in your name, you are considered the stockholder of record with respect to these shares. If you hold your shares in your name as a stockholder of record, you may submit your proxy before the BOC special meeting in one of the following ways:

You may also cast your vote online during the BOC special meeting. Please see “—Attending the BOC Special Meeting” below for further information.

BOC requests that BOC common stockholders vote by telephone, over the Internet or by completing, dating and signing the accompanying proxy and returning it to BOC as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy is returned properly executed, the shares of BOC common stock represented by it will be voted at the BOC special meeting in accordance with the instructions contained on the proxy card. Applicable deadlines for voting by telephone or through the Internet are set forth in your proxy card.

If you hold your BOC common stock in your name as a stockholder of record, and you sign and return your proxy card without indicating how to vote on any particular proposal, the shares of BOC common stock represented by the proxy will be voted “FOR” the merger proposal, “FOR” the BOC stock issuance proposal and “FOR” the BOC adjournment proposal.

If your BOC common stock is held in an account with a bank, broker or other nominee, which are referred to as shares held in “street name,” the bank, broker or other nominee is considered the stockholder of record with respect to these shares and you are the beneficial owner of these “street name” shares.

If your shares are held in “street name” through a bank, broker or other nominee, you will receive instructions from your bank, broker or other nominee that you must follow in order to vote your stock. You should refer to the voting form used by that firm to determine whether you may vote by telephone, Internet or mail.

If your shares are held in “street name,” BOC recommends that you mark, date, sign and promptly mail the voting instruction form provided by your bank, broker or other nominee in accordance with the instructions provided by such nominee. If you do not give your bank, broker or other nominees instructions on how to vote your BOC common stock, your bank, broker or other nominees will not be able to vote your stock on any of the proposals at the BOC special meeting and your shares will not be counted as represented at the BOC special meeting for the purposes of establishing a quorum.

If your shares are held in “street name” through a bank, broker or other nominee you must either direct your nominee on how to vote your stock or obtain a proxy from such nominee to vote online during the BOC special meeting. If your stock is held in “street name,” you may only vote online during the BOC special meeting if you have proof of ownership of your BOC common stock as of the record date and obtain a valid legal proxy from your bank, broker or other nominee that is the stockholder of record of such shares and present such items at the BOC special meeting. Please see “—Attending the BOC Special Meeting” below for further information.

Every stockholder’s vote is important. Accordingly, each BOC common stockholder should promptly submit a proxy, whether or not the stockholder plans to attend the BOC special meeting.

If you are a stockholder of record and your shares are registered in more than one name, you will receive more than one proxy card. If you hold your shares in more than one brokerage account, you may receive a separate voting instruction card for each brokerage account in which you hold stock. In each case, please complete, sign, date and return each proxy card and voting instruction form that you receive.

If your BOC common stock is held in “street name” through a bank, broker or other nominee, you must provide the bank, broker or other nominee, as the stockholder of record of your shares, with instructions on how to vote your shares. Please follow the instructions provided by your bank, broker or other nominee. You may not vote shares held in “street name” by returning a proxy card directly to BOC or by voting online during the BOC special meeting unless you provide a “legal proxy,” which you must obtain from your bank, broker or other nominee.

Brokers, banks or other nominees who hold shares in “street name” for the beneficial owner are not allowed to vote with respect to the approval of matters that are “non-routine” without specific instructions from the beneficial owner. All proposals to be voted on at the BOC special meeting are considered “non-routine” matters and, therefore, brokers, banks and other nominees do not have discretionary voting powers on these matters. A “broker non-vote” occurs on an item when (i) a bank, broker or other nominee has discretionary authority to vote on one or more proposals to be voted on at a meeting of stockholders, but is not permitted to vote on other proposals without instructions from the beneficial owner of the stock and (ii) the beneficial owner fails to provide the bank, broker or other nominee with such instructions. Because none of the proposals to be voted on at the BOC special meeting are routine matters for which brokers may have discretionary authority to vote, there can be no broker non-votes at the BOC special meeting.

Accordingly, if your BOC common stock is held in “street name,” your bank, broker or other nominee will NOT be able to vote your BOC common stock on the BOC merger proposal, the BOC stock issuance proposal or the BOC adjournment proposal unless you have properly instructed your bank, broker or other nominee on how to vote. If you fail to properly instruct your bank, broker or other nominee on how to vote, your shares will not be counted as represented for purposes of establishing a quorum at the BOC special meeting.

If you hold your BOC common stock in your name as a stockholder of record, you may change your vote at any time before your proxy is voted at the BOC special meeting. You may do this in one of four ways:

If you are a BOC stockholder of record and you choose to send a written notice of revocation or to mail a new proxy card, you must submit your notice of revocation or your new proxy to BOC’s corporate secretary at 3 MacArthur Place, Santa Ana, California 92707. The notice of revocation or new proxy card, or electronic proxy submitted via the Internet or by telephone, must be received no later than Tuesday, June 22, 2021, at 5:00 p.m. local time, which is the business day immediately prior to the BOC special meeting.

If your shares are held in “street name” through a bank, broker or other nominee and you have instructed your nominee how to vote your BOC common stock, you must submit new voting instructions to your nominee. You should follow the instructions you receive from your bank, broker or other nominee on how to change or revoke your vote.

The BOC special meeting will be held virtually at http://www.virtualshareholdermeeting.com/BANC2021SM, on Wednesday, June 23, 2021, at 8:00 a.m., local time.

BOC common stockholders as of the close of business on the record date may attend the BOC special meeting online, vote shares electronically and submit questions during the BOC special meeting, by following the instructions on the BOC special meeting website, http://www.virtualshareholdermeeting.com/BANC2021SM. You will need to have your 16-digit control number included on your proxy card to join the BOC special meeting. Online access to the BOC special meeting, which will be an audio-only webcast, will begin at 7:45 a.m., local time, on Wednesday, June 23, 2021.

If your shares are held in “street name” through a bank, broker or other nominee, you may only vote online during the BOC special meeting if you have proof of ownership of your BOC common stock as of the record date and obtain a valid legal proxy from your bank, broker or other nominee that is the stockholder of record of such shares.

Should you need technical support on the day of the BOC special meeting, please call the phone number listed on the virtual meeting landing page on the website, http://www.virtualshareholdermeeting.com/BANC2021SM.

The SEC’s proxy rules permit companies and intermediaries, such as brokers and banks, to satisfy proxy statement delivery requirements for two or more stockholders sharing an address by delivering one proxy statement to those stockholders. This procedure, known as “householding,” reduces the amount of duplicate information that stockholders receive and lowers printing and mailing costs.

If you share an address with another stockholder, you may receive only one set of proxy materials. If you wish to receive a separate copy of proxy materials now or in the future, please request the additional copies by contacting BOC at:

Banc of California, Inc.

The joint proxy statement/prospectus is also available on the Internet at http://www.proxyvote.com. Similarly, if you are receiving multiple copies of the proxy materials and would like to receive only one copy for your household, you should contact your bank, broker or other nominee, or you may contact BOC in the same manner as set forth above.

BOC is soliciting proxies for the BOC special meeting from BOC common stockholders on behalf of its board of directors. BOC will bear all of the costs of the proxy solicitation for the BOC special meeting, including the costs of preparing, printing and mailing this joint proxy statement/prospectus to its stockholders. In addition to solicitations by mail, BOC’s directors, officers and employees may solicit proxies in person or by telephone, email, facsimile or other electronic methods without additional compensation.

BOC will reimburse brokerage firms and other custodians, nominees and fiduciaries for their reasonable out-of-pocket expenses incurred by them in forwarding proxy materials to the beneficial owners of BOC common stock held in “street name” by such persons.

If you have any questions or need assistance in voting your shares, please call BOC Investor Relations at (855) 361-2262.

The PMB special meeting will be held in the first floor Training Room at PMB’s offices at 949 South Coast Drive, Costa Mesa, California 92626, on Wednesday, June 23, 2021, at 9:00 a.m., local time. On or about Friday, May 14, 2021, PMB commenced mailing of this joint proxy statement/prospectus and the enclosed form of proxy to its shareholders entitled to vote at the PMB special meeting.

We expect to hold the PMB special meeting in person, but we continue to monitor the situation regarding COVID-19 closely. Accordingly, we are planning for the possibility that the PMB special meeting may be subject to special precautions, including limitations on the number of participants in one room or other limitations. In that regard, only PMB shareholders will be admitted to the PMB special meeting. No guests will be permitted. For safety and security purposes, you will need to obtain authorization in advance to attend the PMB special meeting in person. To do so, please make your request by mail to PMB at 949 South Coast Drive, Costa Mesa, CA 92626, Attention: Chief Financial Officer, by email at Curt.Christianssen@pmbank.com or by phone at (714) 438-2500. PMB must receive your request for pre-authorization on or before Tuesday, June 15, 2021.

At the PMB special meeting, PMB common shareholders will be asked to consider and vote upon the following proposals:

PMB will transact no other business at the PMB special meeting other than as listed above.

After careful consideration, the PMB board of directors has approved the merger agreement and the transactions contemplated thereby, and determined that the merger agreement and the transactions contemplated thereby are fair to and in the best interests of PMB and its shareholders.

The PMB board of directors recommends that you vote “FOR” the PMB merger proposal, “FOR” the PMB NEO compensation proposal and “FOR” the PMB adjournment proposal. Please see the section entitled “The Merger—Recommendation of the PMB Board of Directors and Reasons for the Merger.”

The PMB board of directors has fixed the close of business on Monday, May 10, 2021 as the record date for determining the holders of PMB common shares entitled to receive notice of and to vote at the PMB special meeting.

As of the close of business on the record date, there were 22,322,184 PMB common shares outstanding and entitled to vote at the PMB special meeting held by 84 shareholders of record. Each PMB voting common share entitles the holder to one vote on each proposal to be considered at the PMB special meeting.

A majority of shares entitled to vote, represented in person or by proxy, constitutes a quorum for transacting business at the PMB special meeting. Abstentions will be counted as represented at the PMB special meeting for purposes of determining the presence or absence of a quorum for all matters voted on at the PMB special meeting.

Since none of the proposals to be voted on at the PMB special meeting are routine matters for which brokers may have discretionary authority to vote, there can be no broker non-votes at the PMB special meeting. Consequently, failure to provide instructions to your bank, broker or other nominee on how to vote will result in your shares not being counted as represented for purposes of establishing a quorum at the PMB special meeting. Please see “—Shares Held in ‘Street Name”’ below for further information.

As of the close of business on the record date, directors and executive officers of PMB and their affiliates owned and were entitled to vote 3,166,347 PMB common shares, representing approximately 14.2% of the PMB common shares outstanding on that date. As of the close of business on the record date, BOC beneficially held no PMB common shares.

In connection with the merger agreement, each of the directors and certain shareholders of PMB have entered into a voting agreement with BOC in which such director or shareholder has agreed to vote all PMB common shares that he or she owns and has the power to vote in favor of the PMB merger proposal and any other matter that is required to be approved by the shareholders of PMB to facilitate the transactions contemplated by the merger agreement. Such persons also agreed to vote against any proposal made in opposition to the approval of the principal terms of the merger agreement or in competition with the merger agreement, against any acquisition proposal and against any proposal, transaction, agreement or amendment to PMB’s organizational documents that is intended or could reasonably be expected to prevent, impede, interfere with, delay, postpone or discourage consummation of the merger. As of the close of business on the record date, such persons beneficially owned, in the aggregate, 2,754,062 PMB common shares, allowing them to exercise approximately 12.3% of the voting power of PMB common shares (which does not include shares issuable upon the exercise of stock options or upon the vesting of PMB RSUs that were not outstanding as of the close of business on the record date).

Approval of each of the proposals to be voted on at the PMB special meeting by the PMB common shareholders will require the following votes:

For purposes of the PMB special meeting, an abstention occurs when a PMB common shareholder attends the PMB special meeting, either in person or represented by proxy, but abstains from voting.

Abstentions will be counted as represented at the PMB special meeting for purposes of determining the presence or absence of a quorum for all matters voted on at the PMB special meeting.

Giving a proxy means that a shareholder authorizes the persons named in the proxy to vote such holder’s shares at the PMB special meeting in the manner such holder directs. A PMB common shareholder may vote by proxy or may vote in person during the PMB special meeting.

The method of voting by proxy differs for shares held by shareholders of record and shares held in “street name.”

If your PMB common shares are registered directly in your name, you are considered the shareholder of record with respect to these shares. If you hold your shares in your name as a shareholder of record, you may submit your proxy before the PMB special meeting in one of the following ways:

You may also cast your vote in person during the PMB special meeting. Please see “—Attending the PMB Special Meeting” below for further information.

PMB requests that PMB common shareholders vote by telephone, over the Internet or by completing, dating and signing the accompanying proxy and returning it to PMB as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy is returned properly executed, the PMB common shares represented by it will be voted at the PMB special meeting in accordance with the instructions contained on the proxy card. Applicable deadlines for voting by telephone or through the Internet are set forth in your proxy card.

If you hold your PMB common shares in your name as a shareholder of record, and you sign and return your proxy card without indicating how to vote on any particular proposal, the PMB common shares represented by the proxy will be voted “FOR” the PMB merger proposal, “FOR” the PMB NEO compensation proposal and “FOR” the PMB adjournment proposal.

If your PMB common shares are held in an account with a bank, broker or other nominee, which are referred to as shares held in “street name,” the bank, broker or other nominee is considered the shareholder of record with respect to these shares and you are the beneficial owner of these “street name” shares.

If your shares are held in “street name” through a bank, broker or other nominee, you will receive instructions from your bank, broker or other nominee that you must follow in order to vote your shares. You should refer to the voting form used by that firm to determine whether you may vote by telephone, Internet or mail.

If your shares are held in “street name,” PMB recommends that you mark, date, sign and promptly mail the voting instruction form provided by your bank, broker or other nominee in accordance with the instructions provided by such nominee. If you do not give your bank, broker or other nominees instructions on how to vote your PMB common shares, your bank, broker or other nominees will not be able to vote your shares on any of the proposals at the PMB special meeting and your shares will not be represented at the PMB special meeting.

If your shares are held in “street name” through a bank, broker or other nominee you must either direct your nominee on how to vote your shares or obtain a proxy from such nominee to vote in person during the PMB special meeting. If your shares are held in “street name,” you may only vote in person during the PMB special meeting if you have proof of ownership of your PMB common shares as of the record date and obtain a valid legal proxy from your bank, broker or other nominee that is the shareholder of record of such shares and present such items at the PMB special meeting. Please see “—Attending the PMB Special Meeting” below for further information.

Every shareholder’s vote is important. Accordingly, each PMB common shareholder should promptly submit a proxy, whether or not the shareholder plans to attend the PMB special meeting.

If you are a shareholder of record and your shares are registered in more than one name, you will receive more than one proxy card. If you hold your shares in more than one brokerage account, you may receive a separate voting instruction card for each brokerage account in which you hold shares. In each case, please complete, sign, date and return each proxy card and voting instruction form that you receive.

If your PMB common shares are held in “street name” through a bank, broker or other nominee, you must provide the bank, broker or other nominee, as the shareholder of record of your shares, with instructions on how to vote your shares. Please follow the instructions provided by your bank, broker or other nominee. You may not vote shares held in “street name” by returning a proxy card directly to PMB or by voting in person during the PMB special meeting unless you provide a “legal proxy,” which you must obtain from your bank, broker or other nominee.

Brokers, banks or other nominees who hold shares in “street name” for the beneficial owner are not allowed to vote with respect to the approval of matters that are “non-routine” without specific instructions from the beneficial owner. All proposals to be voted on at the PMB special meeting are considered “non-routine” matters and, therefore, brokers, banks and other nominees do not have discretionary voting powers on these matters. A “broker non-vote” occurs on an item when (i) a bank, broker or other nominee has discretionary authority to vote on one or more proposals to be voted on at a meeting of shareholders, but is not permitted to vote on other proposals without instructions from the beneficial owner of the shares and (ii) the beneficial owner fails to provide the bank, broker or other nominee with such instructions. Because none of the proposals to be voted on at the PMB special meeting are routine matters for which brokers may have discretionary authority to vote, there can be no broker non-votes at the PMB special meeting.

Accordingly, if your PMB common shares are held in “street name,” your bank, broker or other nominee will NOT be able to vote your PMB common shares on the PMB merger proposal, the PMB NEO compensation proposal or the PMB adjournment proposal, and your shares will not be counted as

represented for purposes of establishing a quorum at the PMB special meeting unless you have properly instructed your bank, broker or other nominee on how to vote.

If you hold your PMB common shares in your name as a shareholder of record, you may change your vote at any time before your proxy is voted at the PMB special meeting. You may do this in one of four ways:

If you are a PMB shareholder of record and you choose to send a written notice of revocation or to mail a new proxy card, you must submit your notice of revocation or your new proxy to PMB’s corporate secretary at 949 South Coast Drive, Suite 300, Costa Mesa, California 92626. The notice of revocation or new proxy card, or electronic proxy submitted via the Internet or by telephone, must be received no later than Tuesday, June 22, 2021, at 5:00 p.m. local time, which is the business day immediately prior to the PMB special meeting.

If your shares are held in “street name” through a bank, broker or other nominee and you have instructed your nominee how to vote your PMB common shares, you must submit new voting instructions to your nominee. You should follow the instructions you receive from your bank, broker or other nominee on how to change or revoke your vote.

The PMB special meeting will be held in the first floor Training Room at PMB’s offices at 949 South Coast Drive, Costa Mesa, California 92626, on Wednesday, June 23, 2021, at 9:00 a.m., local time. We expect to hold the PMB special meeting in person, but we continue to monitor the situation regarding COVID-19 closely. Accordingly, we are planning for the possibility that the PMB special meeting may be subject to special precautions, including limitations on the number of participants in one room or other limitations. In that regard, only PMB shareholders will be admitted to the PMB special meeting. No guests will be permitted. For safety and security purposes, you will need to obtain authorization in advance to attend the PMB special meeting in person. To do so, please make your request by mail to PMB at 949 South Coast Drive, Costa Mesa, CA 92626, Attention: Chief Financial Officer, by email at Curt.Christianssen@pmbank.com or by phone at (714) 438-2500. PMB must receive your request for pre-authorization on or before Tuesday, June 15, 2021.

If your shares are held in “street name” through a bank, broker or other nominee, you may only vote in person during the PMB special meeting if you have proof of ownership of your PMB common shares as of the record date and obtain a valid legal proxy from your bank, broker or other nominee that is the shareholder of record of such shares.

In connection with the merger, under the CGCL, PMB shareholders are not entitled to exercise dissenters’ rights.

The SEC’s proxy rules permit companies and intermediaries, such as brokers and banks, to satisfy proxy statement delivery requirements for two or more shareholders sharing an address by delivering one proxy statement to those shareholders. This procedure, known as “householding,” reduces the amount of duplicate information that shareholders receive and lowers printing and mailing costs.

If you share an address with another shareholder, you may receive only one set of proxy materials. If you wish to receive a separate copy of proxy materials now or in the future, please request the additional copies by sending a request to Computershare Investor Services, P.O. Box 505005, Louisville, KY 40233-5005 or Computershare Investor Services, 462 South 4^th Street, Suite 1600, Louisville, KY 40202. The joint proxy statement/prospectus is also available on the Internet at http://www.edocumentview.com/PMBC. Similarly, if you are receiving multiple copies of the proxy materials and would like to receive only one copy for your household, you should contact your bank, broker or other nominee, or you may contact Computershare in the same manner as set forth above.

PMB is soliciting proxies for the PMB special meeting from PMB common shareholders on behalf of its board of directors. PMB will bear all of the costs of the proxy solicitation for the PMB special meeting, including the costs of preparing, printing and mailing this joint proxy statement/prospectus to its shareholders. In addition to solicitations by mail, PMB’s directors, officers and employees may solicit proxies in person or by telephone, email, facsimile or other electronic methods without additional compensation.

PMB will reimburse brokerage firms and other custodians, nominees and fiduciaries for their reasonable out-of-pocket expenses incurred by them in forwarding proxy materials to the beneficial owners of PMB common shares held in “street name” by such persons.

If you have any questions or need assistance in voting your shares, please call PMB Investor Relations at (714) 438-2531.

As discussed throughout this joint proxy statement/prospectus, BOC is asking its common stockholders to approve the BOC merger proposal. Holders of BOC common stock should read carefully this document in its entirety, including the appendices, for more detailed information concerning the merger agreement and the merger. In particular, holders of BOC common stock are directed to the merger agreement, a copy of which is attached as Appendix A to this joint proxy statement/prospectus.

The BOC board of directors recommends a vote “FOR” the BOC merger proposal.

As discussed throughout this joint proxy statement/prospectus, BOC is asking its stockholders to approve the issuance of BOC common stock in connection with the merger.

The BOC board of directors recommends a vote “FOR” the BOC stock issuance proposal.

The BOC special meeting may be adjourned to another time and place, if necessary or appropriate, to permit, among other things, the further solicitation of proxies if there are insufficient votes at the time of the BOC special meeting to approve the BOC merger proposal or the BOC stock issuance proposal.

If, at the special meeting, BOC does not have sufficient votes to approve the BOC merger proposal or the BOC stock issuance proposal, BOC intends to move to adjourn the BOC special meeting in order to enable the board of directors to solicit additional proxies. If the common stockholders approve the BOC adjournment proposal, BOC could adjourn the BOC special meeting and use the additional time to solicit additional proxies, including the solicitation of proxies from common stockholders who have previously voted.

The BOC board of directors recommends a vote “FOR” the BOC adjournment proposal.

Pursuant to Section 2-502 of the Maryland General Corporation Law, referred to as the MGCL, BOC may not transact any other business at the BOC special meeting other than as listed above.

As discussed throughout this joint proxy statement/prospectus, PMB is asking its common shareholders to approve the PMB merger proposal. Holders of PMB common shares should read carefully this document in its entirety, including the appendices, for more detailed information concerning the merger agreement and the merger. In particular, holders of PMB common shares are directed to the merger agreement, a copy of which is attached as Appendix A to this joint proxy statement/prospectus.

The PMB board of directors recommends a vote “FOR” the PMB merger proposal.

Pursuant to Section 14A of the Exchange Act, and Rule 14a-21(c) promulgated thereunder, PMB is seeking a non-binding, advisory shareholder approval of the compensation to be paid to the named executive officers of PMB in connection with the merger. The proposal gives PMB’s common shareholders the opportunity to express their views on the merger-related compensation of the named executive officers of PMB.

Accordingly, PMB is asking PMB’s common shareholders to vote “FOR” the adoption of the following resolution, on a non-binding, advisory basis:

“RESOLVED, that the compensation that may be paid or become payable to PMB’s named executive officers, in connection with the merger, and the agreements or understandings pursuant to which such compensation may be paid or become payable, in each case as disclosed pursuant to Item 402(t) of Regulation S-K in ‘The Merger—Interests of PMB’s Directors and Executive Officers in the Merger and ‘The Merger—Merger-Related Compensation for PMB’s Named Executive Officers’ are hereby APPROVED.”

The advisory vote on the PMB NEO compensation proposal is a vote separate and apart from the votes on the PMB merger proposal and the PMB adjournment proposal. Accordingly, PMB common shareholders may vote to approve the PMB merger proposal and/or the PMB adjournment proposal and vote not to approve the PMB NEO compensation proposal, and vice versa. The approval of the PMB NEO compensation proposal is not a condition to the consummation of the merger. If the merger is completed, the merger-related compensation will be paid to the named executive officers of PMB to the extent payable in accordance with the terms of the compensation agreements or arrangements even if PMB’s common shareholders fail to approve the advisory vote regarding merger-related compensation.

The PMB board of directors recommends a vote “FOR” the PMB NEO compensation proposal.

The PMB special meeting may be adjourned to another time and place, if necessary or appropriate, to permit, among other things, the further solicitation of proxies if there are insufficient votes at the time of the PMB special meeting to approve the PMB merger proposal.

If, at the PMB special meeting, PMB does not have the affirmative vote of a majority of the outstanding shares entitled to vote to approve the PMB merger proposal or the PMB NEO compensation proposal, PMB intends to move to adjourn the PMB special meeting in order to enable the board of directors to solicit additional proxies for approval of the PMB merger proposal or the PMB NEO compensation proposal. If the common shareholders approve the PMB adjournment proposal, PMB could adjourn the PMB special meeting and use the additional time to solicit additional proxies, including the solicitation of proxies from common shareholders who have previously voted.

The PMB board of directors recommends a vote “FOR” the PMB adjournment proposal.

Under Section 601(a) of the CGCL, PMB may not transact any other business at the PMB special meeting other than as listed above.

Banc of California, Inc.

Banc of California, Inc., a Maryland corporation, is a bank holding company registered under the Bank Holding Company Act of 1956, as amended, referred to as the BHC Act, with corporate headquarters in Santa Ana, California. BOC’s principal business is to serve as the holding company for BOC’s wholly owned subsidiary, Banc of California, National Association, a national banking association. References to BOC refer to BOC together with BOC Bank and its other subsidiaries on a consolidated basis.

BOC is a relationship-focused business bank that delivers comprehensive products and solutions for businesses, business owners and individuals. It offers a full array of competitively priced and client-tailored loan and deposit products and services through 29 full service branches extending from San Diego to Santa Barbara. It also offers commercial loan products, including commercial and industrial loans, commercial real estate loans and multifamily loans, SBA loans, construction loans and other consumer loans. In addition, BOC has a SFR mortgage loan portfolio that it services.

As of March 31, 2021, on a consolidated basis, BOC had total assets of $7.9 billion, total loans of $5.8 billion, total deposits of $6.1 billion, and stockholders’ equity of $804.7 million.

BOC’s common stock is traded on the NYSE under the symbol “BANC.”

Additional information about BOC and its subsidiaries may be found in the documents incorporated by reference into this document. Please also see the section entitled “Where You Can Find More Information.”

Pacific Mercantile Bancorp

Pacific Mercantile Bancorp is the parent holding company of Pacific Mercantile Bank, which opened for business March 1, 1999. PM Bank, which is an FDIC insured, California state-chartered bank and a member of the Federal Reserve System, provides a wide range of commercial banking services to businesses, business professionals and individual clients. PM Bank is headquartered in Orange County and operates a total of seven offices in Southern California, located in Orange, Los Angeles, San Diego, and San Bernardino counties. PM Bank offers tailored flexible solutions for its clients including an array of loan and deposit products, sophisticated cash management services, and comprehensive online banking services.

PM Bank’s commercial lending solutions include working capital lines of credit and asset based lending, 7(a) and 504 Small Business Administration loans, commercial real estate loans, growth capital loans, equipment financing, letters of credit and corporate credit cards. PM Bank’s depository and corporate banking services include cash and treasury management solutions, interest-bearing term deposit accounts, checking accounts, automated clearinghouse payment and wire solutions, fraud protection, remote deposit capture, courier services and online banking. PM Bank serves clients operating in a global marketplace through services including letters of credit and import/export financing. PMB has developed its Horizon Analytics tool which provides financial modeling and analysis to help its customers succeed.

As of March 31, 2021, on a consolidated basis, PMB had total assets of $1.6 billion, total loans of $1.2 billion, total deposits of $1.4 billion and total shareholders’ equity of $161.3 million.

PMB’s common stock is traded on Nasdaq under the symbol “PMBC.”

Additional information about PMB and its subsidiaries may be found in the documents incorporated by reference into this document. Please see the section entitled “Where You Can Find More Information.”

The following is a discussion of the merger and the material terms of the merger agreement between BOC and PMB. You are urged to read carefully the merger agreement in its entirety, a copy of which is attached as Appendix A to this document and incorporated by reference herein. This summary does not purport to be complete and may not contain all of the information about the merger agreement that is important to you. In addition, important business and financial information about each of BOC and PMB can be found elsewhere in this document and in the public filings BOC and PMB make with the SEC, as described in the section entitled “Where You Can Find More Information.”

BOC’s board of directors has approved the merger and PMB’s board of directors has approved the principal terms of the merger agreement. The merger agreement provides for the merger of PMB with and into BOC, with BOC continuing as the surviving corporation. Promptly after the merger, PM Bank will merge with and into BOC Bank, with BOC Bank as the surviving bank.

In the merger, each PMB common share, other than specified excluded shares described under “The Merger Agreement—Merger Consideration—Cancellation of Excluded Shares,” will be converted into the right to receive 0.50 of a share of BOC common stock. For each fractional share that would otherwise be issued, BOC will pay cash in an amount equal to the fraction of a share of BOC common stock which the holder would otherwise be entitled to receive multiplied by the BOC average closing price (determined as the volume weighted average price of shares of BOC common stock quoted on the NYSE on each of the last 20 trading days ending on the day which is the fifth trading day immediately preceding the date that the effective time occurs).

The market value of the merger consideration will fluctuate with the price of BOC common stock, and the value of the shares of BOC common stock that holders of PMB common shares will receive upon consummation of the merger may be different than the value of the shares of BOC common stock that holders of PMB common shares would receive if calculated on the date BOC and PMB announced the merger agreement, on the date that this document is being mailed to PMB shareholders and to BOC stockholders, and on the date of the BOC special meeting or PMB special meeting. Based on the closing price of BOC common stock on March 22, 2021, the value of the per share merger consideration payable to holders of PMB common shares was $9.77. Based on the closing price of BOC common stock on May 10, 2021, the last practicable date before the date of this document, the value of the per share merger consideration payable to holders of PMB common shares was $8.86.

PMB Stock Options. At the effective time, each PMB stock option that is outstanding immediately prior to the effective time, whether vested or unvested, will be cancelled and will entitle the holder thereof to receive an amount in cash equal to the product of (i) the total number of PMB common shares subject to such option and (ii) the excess, if any, of (A) an amount equal to the product of the BOC average closing price and 0.50 over (B) the exercise price per PMB common share underlying such option, less any applicable taxes required to be withheld with respect to such payment. Any PMB stock options which have an exercise price per share that is greater than or equal to the product of the BOC average closing price and 0.50 will be cancelled at the effective time of the merger for no consideration or payment.

PMB Restricted Shares and RSUs. At the effective time of the merger, each PMB restricted share and each PMB RSU will, automatically and without any action on the part of the holder of such PMB restricted shares or PMB RSUs, accelerate in full, be cancelled and will only entitle the holder of such PMB restricted shares or PMB RSUs to receive, on the first regular payroll date following the closing date of the merger, an amount in cash equal to the product of (i) such holder’s total number of PMB restricted shares or RSUs, as applicable, and (ii) an amount equal to the product of the BOC average closing price and 0.50, less any applicable taxes required to be withheld with respect to such vesting, which tax withholding may, at the election of the holder, be effected by deduction from such cash amount equal to the amount of taxes to be withheld.

The PMB board of directors regularly reviews its business strategies, opportunities and challenges as a part of its consideration and evaluation of its long-term prospects, with the goal of enhancing shareholder value. The considerations have focused on, among other things, the competitive landscape as well as the business and regulatory environment facing financial institutions generally and PMB in particular. The PMB board of directors has also considered, from time to time, various potential strategic alternatives, including transactions with other financial institutions, such as potential acquisitions of smaller financial institutions, mergers with financial institutions of similar size, or combinations with larger financial institutions. BOC’s management and board of directors also regularly reviews its business strategies and opportunities. Over the last two years, BOC’s strategy has focused on transforming the institution into a relationship-focused business bank, with a longer-term view of further enhancing the value of the BOC franchise through acquisitions.

Over time and in response to informal inquiries regarding PMB’s willingness to engage in a strategic business combination, Denis Kalscheur, PMB’s chairman, and Brad Dinsmore, PMB’s chief executive officer, each met or held discussions with representatives of a number of financial institutions regarding potential interest in a business combination, including representatives of BOC.

In December 2020 and the first half of January 2021, Mr. Kalscheur held informal discussions with the chief executive officers of BOC and another potential acquirer of PMB, which we refer to as Party B, regarding the potential benefits of a business combination. No specific terms of a potential combination were discussed at these meetings. Mr. Kalscheur provided the PMB board of directors with an update on these initial discussions at a board meeting on January 20, 2021. This meeting was attended by representatives of KBW, a nationally recognized investment banking firm with substantial expertise in transactions involving financial institutions similar to PMB, and Sheppard, Mullin, Richter & Hampton LLP, which we refer to as Sheppard Mullin, counsel to PMB. KBW discussed, among other things, the franchise characteristics, financial performance and financial ability to pay in a potential acquisition of PMB of both BOC and Party B based on publicly available information, and Sheppard Mullin reviewed the fiduciary duties of the PMB board of directors in connection with its consideration of a proposed business combination. At this meeting, the PMB board of directors was advised that Patriot Financial Partners, L.P., referred to as Patriot Financial, of which PMB director James Deutsch is a partner, has one or more affiliated investment funds that own non-controlling interests in each of BOC and Party B. As a result, it was determined that Mr. Deutsch would abstain from any vote on a potential business combination involving either party. Also at this meeting, the PMB board of directors formed a special committee comprised entirely of independent directors to review and assess one or more potential business combinations in the context of PMB’s strategic alternatives and to make recommendations to the full board. The PMB special committee was composed of directors Kalscheur, Hoopis and Miyakawa.

On January 25, 2021, the BOC board of directors held a meeting at which Jared Wolff, BOC’s chief executive officer, presented to the board on certain strategic matters, including a potential business combination with PMB. The BOC board of directors determined to establish a committee of the board, consisting of Mr. Wolff, Conan Barker, Mary Curran, Richard Lashley and Robert Sznewajs, in respect of certain matters related to the proposed combination. In addition, Mr. Wolff discussed the fact that Patriot Financial, of which BOC director W. Kirk Wycoff is a managing partner, has an affiliated investment fund that owns a non-controlling interest in PMB. As a result, it was determined that Mr. Wycoff would abstain from any vote on a potential business combination involving PMB.

On January 28, 2021 and January 29, 2021, the PMB special committee met to review and consider several preliminary discussions with BOC and Party B that had occurred since the last PMB board meeting, as well as the advisability of reaching out to other potential merger partners. Representatives from KBW attended both meetings and again discussed a potential merger between PMB and each of BOC and Party B.

On January 29, 2021, at the direction of the PMB special committee, KBW contacted BOC and Party B and sent each party a proposed non-disclosure agreement. Each of BOC and PMB negotiated and executed a non-disclosure agreement on January 30, 2021. Between January 30, 2021 and February 1, 2021, representatives of BOC and PMB management as well as representatives of KBW discussed various matters, including valuation and the exchange ratio at which PMB would consider a potential transaction with BOC. On February 1, 2021, BOC’s chief executive officer sent a non-binding indication of interest which included a requirement for exclusivity should PMB be interested in pursuing a potential transaction. The BOC indication of interest contemplated a merger of PMB into BOC in which PMB shareholders would receive shares of BOC at a fixed

exchange ratio of 0.5 of a share of BOC common stock per share of PMB common stock, which implied a value of $8.64 per PMB share based on BOC’s closing stock price on February 1, 2021. On that date, PMB’s closing stock price was $5.89 per share.

On February 2, 2021, the PMB special committee met to consider the indication of interest from BOC. Representatives of both KBW and Sheppard Mullin also attended this meeting. A representative of KBW reviewed BOC’s proposal with the PMB special committee, including financial aspects of BOC’s proposal. After review of the indication and its components, the PMB special committee determined it was in the best interest of all shareholders to pursue BOC’s proposed transaction because of the initial premium it placed on PMB and the potential upside in value in the combined company. The PMB special committee instructed KBW and Sheppard Mullin to identify and discuss with BOC several points in the indication of interest and to communicate to BOC that, if the PMB special committee and BOC could reach a mutually acceptable agreement on the indication of interest, the PMB special committee would recommend to the full board of directors that PMB enter into exclusivity with BOC. On February 2, 2021 and February 3, 2021, representatives of Sheppard Mullin and KBW identified and discussed with BOC the points raised by the PMB special committee regarding the indication of interest from BOC, which BOC agreed to revise. The points included, among others, the nature of the post-closing restrictive covenants to be required of certain PMB executives, the number of PMB directors to be invited to join the BOC board upon closing, and a BOC proposed closing condition related to the level of PMB’s allowance for loan and lease losses at closing.

On February 4, 2021, the PMB board of directors convened a special meeting. At this meeting, a representative of KBW reviewed (i) the terms of the BOC indication of interest, (ii) publicly available information regarding other, larger financial institutions potentially having an interest in PMB, including Party B, and (iii) a comparison of the BOC indication of interest to other transactions. The PMB board of directors also discussed with the KBW representative the alternative of PMB continuing operations on a standalone basis. After extensive discussion regarding the strategic options available to PMB, the other financial institutions that were believed to potentially have an interest in a business combination with PMB, and the benefits of a transaction with BOC, the PMB Board determined that it would be inadvisable to solicit additional offers from other institutions and agreed (with Mr. Deutsch abstaining) with the PMB special committee’s recommendation to pursue a potential transaction with BOC on an exclusive basis. Later that day, PMB entered into an exclusivity agreement with BOC pursuant to which it would allow the parties to complete due diligence and negotiate exclusively for a period of 45 days. At the direction of the PMB board of directors, KBW informed Party B that PMB was moving in a different strategic direction and would reach out to Party B if PMB decided to continue exploring a potential transaction with Party B.

On February 4, 2021, at a regularly scheduled meeting of the BOC board of directors, Mr. Wolff updated the BOC board of directors on the potential transaction with PMB, including that the parties had entered into a 45-day exclusivity period.

On February 23, 2021, representatives of Sullivan & Cromwell LLP, which we refer to as Sullivan & Cromwell, counsel to BOC, provided representatives of Sheppard Mullin with an initial draft of the merger agreement. On February 24, 2021, the PMB special committee convened a meeting to review the draft merger agreement. Mr. Dinsmore updated the special committee on the status of discussions with BOC, and representatives of Sheppard Mullin outlined for the special committee the material terms of the agreement, including the merger consideration, transaction structure, conditions to closing, operating and restrictive covenants and execution risks. This meeting was also attended by representatives of KBW.

Between February 23, 2021 and March 22, 2021, representatives of PMB and BOC, together with representatives of Sheppard Mullin and Sullivan & Cromwell, negotiated the specific terms and exchanged drafts of the merger agreement and related ancillary documents, which were finalized on or shortly before March 22, 2021. Certain key items negotiated included, among others, the representations and warranties to be provided by BOC to PMB in the merger agreement, the restrictive covenants applicable to each of PMB and BOC between signing and closing, the condition to BOC’s obligation to close related to PMB’s allowance for lease losses and shareholders’ equity at closing, and the duration of the post-closing restrictive covenants to be provided by certain members of PMB executive management. Also during that time and the time from the date of the exclusivity agreement, members of BOC management continued and finalized their due diligence review of PMB and members of PMB management conducted a due diligence review of BOC.

On March 16, 2021, Mr. Wolff and the BOC special committee held a meeting to discuss the status of the proposed merger, the negotiations concerning the draft definitive agreements, and certain due diligence matters, including in respect of certain PMB credit matters. Between March 16, 2021 and March 22, 2021, representatives of BOC and PMB continued to discuss these diligence matters and negotiate the final terms of the definitive agreement, including the condition to BOC’s obligation to close related to PMB’s allowance for loan and lease losses and shareholders’ equity at closing, and the duration of the post-closing restrictive covenants to be provided by certain members of PMB executive management.

On March 19, 2021, the PMB special committee held a meeting at which representatives from Sheppard Mullin and KBW were present. At that meeting, the PMB special committee reviewed the material terms of the merger agreement and related ancillary documents with a representative of Sheppard Mullin and a representative of KBW reviewed the financial aspects of the proposed transaction, which included a review of the financial analyses it would perform in connection with delivery of an opinion. The PMB special committee concluded at that meeting to recommend to the PMB board of directors that it proceed with the transaction with BOC.

Also on March 19, 2021, the BOC board of directors met to review the proposed merger agreement and related ancillary documents, copies of which were provided to the directors in advance of the meeting. Representatives of Sullivan & Cromwell and Piper Sandler also attended the meeting. Among other things, Mr. Wolff discussed with the BOC board members the terms of the proposed combination, the negotiations to date, and the due diligence undertaken by BOC and its advisors in respect of PMB. Representatives of Piper Sandler then reviewed the financial aspects of the proposed merger, including discussing the various financial methodologies used in the Piper Sandler analysis, following which Piper Sandler rendered to the BOC board of directors its opinion, which was subsequently confirmed in writing on March 19, 2021, to the effect that, as of such date, the merger consideration was fair to BOC from a financial point of view. At this meeting, a representative of Sullivan & Cromwell also reminded the BOC board of directors of the discussion of fiduciary duties they had held in December 2020, and then reviewed with the BOC board of directors the material terms of the proposed draft definitive agreements. After extensive discussion regarding the terms of the merger agreement and the related ancillary agreements, and taking into consideration the matters described under “The Merger—Recommendation of the BOC Board of Directors and Reasons for the Merger” among others, Mr. Wycoff left the meeting and the remaining members of the BOC board of directors unanimously approved the merger agreement and the merger and determined to recommend that BOC stockholders approve the merger agreement and the issuance of shares to PMB shareholders in the merger.

On March 22, 2021, the PMB board of directors met to review the proposed merger agreement and related ancillary documents, copies of which were provided to the directors in advance of the meeting. Representatives from Sheppard Mullin also attended the meeting and reviewed with the board its fiduciary duties and reviewed in detail the terms of the proposed merger agreement and related ancillary documents. Mr. Dinsmore summarized the results of management’s due diligence review of BOC and reviewed the strategic rationale and anticipated benefits of the proposed merger. Also at this meeting, KBW reviewed the financial aspects of the proposed merger, including discussing the financial analyses performed in connection with its opinion and rendered to the PMB board of directors its opinion (which was initially rendered verbally and subsequently confirmed in a written opinion dated March 22, 2021) to the effect that, as of such date and subject to the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by KBW as set forth in its opinion, the exchange ratio in the proposed merger was fair, from a financial point of view, to the holders of PMB common stock. After extensive discussion regarding the terms of the merger agreement and the related ancillary agreements, a full analysis of PMB’s reasons for the engaging in the proposed business combination with BOC, including those set forth below under “The Merger—Recommendation of the PMB Board of Directors and Reasons for the Merger,” and consideration of other relevant issues, including a variety of business, financial and market factors, the PMB board of directors unanimously (with Mr. Deutsch abstaining) adopted and approved the merger agreement and the merger and determined to recommend that PMB shareholders approve the principal terms of the merger agreement.

Following the BOC board meeting on March 19, 2021 and the PMB board meeting on March 22, 2021, PMB and BOC entered into the merger agreement and announced the merger on March 22, 2021.

In reaching its decision to approve the merger agreement, the merger and the other transactions contemplated by the merger agreement, the BOC board of directors evaluated the merger agreement in consultation with BOC senior management, as well as BOC’s legal counsel and financial advisor, and considered a number of factors, including the following:

The BOC board of directors also considered the potential adverse consequences of, and risks associated with, the proposed merger, including:

The foregoing discussion of the information and factors considered by the BOC board of directors is not intended to be exhaustive, but includes the material factors considered by the BOC board of directors. In reaching its decision to approve the merger agreement, the merger and the other transactions contemplated by the merger agreement, the BOC board of directors did not quantify or assign any relative weights to the factors considered, and individual directors may have given different weights to different factors. The BOC board of directors considered all these factors as a whole, including discussions with, and questioning of, BOC’s senior management and BOC’s advisors, and overall considered the factors to be favorable to, and to support its determination to approve entering into the merger agreement.

This explanation of BOC’s reasons for the merger and other information presented in this section is forward-looking in nature and should be read in light of the section entitled “Cautionary Statement Regarding Forward-Looking Statements.”

BOC’s board of directors realized that there can be no assurance about future results, including results expected or considered in the factors listed above, such as assumptions regarding enhanced business prospects, anticipated cost savings and earnings accretion/dilution. The BOC board of directors concluded, however, that the potential positive factors outweighed the potential risks of completing the transaction.

For the reasons set forth above, the BOC board of directors determined that the merger, the merger agreement and the transaction contemplated thereby are advisable and fair to and in the best interests of BOC and its stockholders, and has approved the merger. The BOC board of directors recommends that BOC stockholders vote “FOR” the BOC merger proposal, “FOR” the BOC stock issuance proposal and “FOR the BOC adjournment proposal.

In reaching its decision to approve the merger agreement and the transactions contemplated thereby, the PMB board of directors evaluated the merger agreement in consultation with PMB executive management, as well as PMB’s legal counsel and financial advisor, and considered numerous factors, including the following:

The PMB board of directors also considered the potential adverse consequences of, and risks associated with, the proposed merger, including:

The foregoing discussion of information and factors considered by the PMB board of directors is not intended to be exhaustive. In light of the variety of factors considered in connection with its evaluation of the merger agreement and the transactions contemplated thereby, the PMB board of directors did not find it practicable to, and did not, quantify or otherwise assign relative weights to the specific factors considered in reaching its determinations and recommendations. Moreover, each member of the PMB board of directors applied his or her own personal business judgment to the process and may have given different weight to different factors than other members gave to such factors.

For the reasons set forth above, the PMB board of directors determined that the merger is advisable and in the best interests of PMB shareholders and approved the merger agreement and the transactions contemplated by the merger agreement, including the merger. The PMB board of directors recommends that the PMB shareholders vote “FOR” the PMB merger proposal, “FOR” the PMB NEO compensation proposal, and “FOR” the PMB adjournment proposal.

BOC retained Piper Sandler to act as financial advisor to the BOC board of directors in connection with BOC’s consideration of a possible business combination with PMB. BOC selected Piper Sandler to act as its financial advisor because Piper Sandler is a nationally recognized investment banking firm whose principal business specialty is financial institutions. In the ordinary course of its investment banking business, Piper Sandler is regularly engaged in the valuation of financial institutions and their securities in connection with mergers and acquisitions and other corporate transactions.

Piper Sandler acted as an independent financial advisor to the BOC board of directors in connection with the proposed merger and participated in certain of the negotiations leading to the execution of the merger agreement. At the March 19, 2021, meeting at which the BOC board of directors considered the merger agreement, Piper

Sandler delivered to the BOC board of directors its oral opinion, which was subsequently confirmed in writing on March 19, 2021, to the effect that, as of such date, the merger consideration was fair to BOC from a financial point of view. The full text of Piper Sandler’s opinion is attached as Appendix E to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by Piper Sandler in rendering its opinion. The description of the opinion set forth below is qualified in its entirety by reference to the full text of the opinion. Holders of BOC common stock are urged to read the entire opinion carefully in connection with their consideration of the proposed merger.

Piper Sandler’s opinion was directed to the board of directors of BOC in connection with the board’s consideration of the merger agreement and the merger and does not constitute a recommendation to any stockholder of BOC as to how any such stockholder should vote at any meeting of stockholders called to consider and vote upon the approval of the merger agreement and the merger. Piper Sandler’s opinion was directed only to the fairness, from a financial point of view, of the merger consideration to BOC and did not address the underlying business decision of BOC to engage in the merger, the form or structure of the merger or any other transactions contemplated in the merger agreement, the relative merits of the merger as compared to any other alternative transactions or business strategies that might exist for BOC, or the effect of any other transaction in which BOC might engage. Piper Sandler also did not express any opinion as to the fairness of the amount or nature of the compensation to be received in the merger by any officer, director or employee of BOC or PMB, or any class of such persons, if any, relative to the compensation to be received by any other stockholder. Piper Sandler’s opinion was approved by Piper Sandler’s fairness opinion committee.

In connection with its opinion, Piper Sandler reviewed and considered, among other things:

Piper Sandler also discussed with certain members of the senior management of BOC and its representatives the business, financial condition, results of operations and prospects of BOC and held similar discussions with certain members of the management of PMB and its representatives regarding the business, financial condition, results of operations and prospects of PMB.

In performing its review, Piper Sandler relied upon the accuracy and completeness of all of the financial and other information that was available to Piper Sandler from public sources, that was provided to Piper Sandler by BOC or its representatives, or that was otherwise reviewed by Piper Sandler, and Piper Sandler assumed such accuracy and completeness for purposes of rendering its opinion without any independent verification or investigation. Piper Sandler further relied on the assurances of the senior management of BOC that they were not aware of any facts or circumstances that would have made any of such information inaccurate or misleading in any respect to Piper Sandler’s analysis. Piper Sandler was not asked to and did not undertake, an independent verification of any of such information and Piper Sandler did not assume any responsibility or liability for the accuracy or completeness thereof. Piper Sandler did not make an independent evaluation or perform an appraisal of the specific assets, the collateral securing assets or the liabilities (contingent or otherwise) of BOC or PMB. Piper Sandler rendered no opinion or evaluation on the collectability of any assets or the future performance of any loans of BOC or PMB. Piper Sandler did not make an independent evaluation of the adequacy of the allowance for loan losses of BOC or PMB, or the combined entity after the merger, and Piper Sandler did not review any individual credit files related to BOC or PMB. Piper Sandler assumed, with BOC’s consent, that the respective allowances for loan losses for both BOC and PMB were adequate to cover such losses and would be adequate on a pro forma basis for the combined entity.

In preparing its analyses, Piper Sandler used publicly available mean analyst earnings per share estimates for BOC for the years ending December 31, 2021 and December 31, 2022 with an estimated long-term annual asset and earnings per share growth rate for BOC for the years ending December 31, 2023, December 31, 2024 and December 31, 2025, as well as estimated dividends per share for BOC for the years ending December 31, 2021 through December 31, 2025, as provided by the senior management of BOC. In addition, Piper Sandler used publicly available mean analyst net income estimates for PMB for the years ending December 31, 2021 and December 31, 2022, as well as an estimated long-term annual asset and earnings per share growth rate for the years ending December 31, 2023, December 31, 2024 and December 31, 2025 and estimated dividends per share for PMB for the years ending December 31, 2021 through December 31, 2025, as provided by the senior management of BOC. Piper Sandler also received and used in its pro forma analyses certain assumptions relating to transaction expenses, purchase accounting adjustments and cost savings, as provided by the senior management of BOC. With respect to the foregoing information, the senior management of BOC confirmed to Piper Sandler that such information reflected (or, in the case of the analyst estimates referred to above, were consistent with) the best currently available projections, estimates and judgments of senior management as to the future financial performance of BOC and PMB, respectively, and Piper Sandler assumed that the financial results reflected in such information would be achieved. Piper Sandler expressed no opinion as to such estimates or judgements, or the assumptions on which such information was based. Piper Sandler also assumed that there had been no material change in BOC’s or PMB’s assets, financial condition, results of operations, business or prospects since the date of the most recent publicly available financial statements provided to Piper Sandler. Piper Sandler assumed in all respects material to its analyses that BOC and PMB would remain as going concerns for all periods relevant to its analyses.

Piper Sandler also assumed, with BOC’s consent, that (i) each of the parties to the merger agreement would comply in all material respects with all material terms and conditions of the merger agreement and all related agreements required to effect the merger, that all of the representations and warranties contained in such agreements were true and correct in all material respects, that each of the parties to such agreements would perform in all material respects all of the covenants and other obligations required to be performed by such party under such agreements and that the conditions precedent in such agreements were not and would not be waived, (ii) in the course of obtaining the necessary regulatory or third party approvals, consents and releases with respect to the merger, no delay, limitation, restriction or condition would be imposed that would have an adverse effect on BOC, PMB, the merger or any related transactions, and (iii) the merger and any related transactions would be consummated in accordance with the terms of the merger agreement without any waiver, modification or amendment of any material term, condition or agreement thereof and in compliance with all applicable laws

and other requirements. Finally, with BOC’s consent, Piper Sandler relied upon the advice that BOC received from its legal, accounting and tax advisors as to all legal, accounting and tax matters relating to the merger and the other transactions contemplated by the merger agreement. Piper Sandler expressed no opinion as to any such matters.

Piper Sandler’s opinion was necessarily based on financial, economic, regulatory, market and other conditions as in effect on, and the information made available to Piper Sandler as of, the date thereof. Events occurring after the date thereof could materially affect Piper Sandler’s opinion. Piper Sandler has not undertaken to update, revise, reaffirm or withdraw its opinion or otherwise comment upon events occurring after the date thereof. Piper Sandler expressed no opinion as to the trading value of BOC common stock or PMB common stock at any time or what the value of BOC common stock would be once it is actually received by the holders of PMB common stock.

In rendering its opinion, Piper Sandler performed a variety of financial analyses. The summary below is not a complete description of all the analyses underlying Piper Sandler’s opinion or the presentation made by Piper Sandler to the BOC board of directors, but is a summary of the material analyses performed and presented by Piper Sandler. The summary includes information presented in tabular format. In order to fully understand the financial analyses, these tables must be read together with the accompanying text. The tables alone do not constitute a complete description of the financial analyses. The preparation of a fairness opinion is a complex process involving subjective judgments as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances. The process, therefore, is not necessarily susceptible to a partial analysis or summary description. Piper Sandler believes that its analyses must be considered as a whole and that selecting portions of the factors and analyses to be considered without considering all factors and analyses, or attempting to ascribe relative weights to some or all such factors and analyses, could create an incomplete view of the evaluation process underlying its opinion. Also, no company included in Piper Sandler’s comparative analyses described below is identical to BOC or PMB and no transaction is identical to the merger. Accordingly, an analysis of comparable companies or transactions involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies and other factors that could affect the public trading values or transaction values, as the case may be, of BOC and PMB and the companies to which they were compared. In arriving at its opinion, Piper Sandler did not attribute any particular weight to any analysis or factor that it considered. Rather, Piper Sandler made qualitative judgments as to the significance and relevance of each analysis and factor. Piper Sandler did not form an opinion as to whether any individual analysis or factor (positive or negative) considered in isolation supported or failed to support its opinion, rather, Piper Sandler made its determination as to the fairness of the merger consideration to BOC from a financial point of view on the basis of its experience and professional judgment after considering the results of all its analyses taken as a whole.

In performing its analyses, Piper Sandler also made numerous assumptions with respect to industry performance, business and economic conditions and various other matters, many of which cannot be predicted and are beyond the control of BOC, PMB, and Piper Sandler. The analyses performed by Piper Sandler are not necessarily indicative of actual values or future results, both of which may be significantly more or less favorable than suggested by such analyses. Piper Sandler prepared its analyses solely for purposes of rendering its opinion and provided such analyses to the BOC board of directors at its March 19, 2021 meeting. Estimates on the values of companies do not purport to be appraisals or necessarily reflect the prices at which companies or their securities may actually be sold. Such estimates are inherently subject to uncertainty and actual values may be materially different. Accordingly, Piper Sandler’s analyses do not necessarily reflect the value of BOC common stock or PMB common stock or the prices at which BOC or PMB common stock may be sold at any time. The analyses of Piper Sandler and its opinion were among a number of factors taken into consideration by the BOC board of directors in making its determination to approve the merger and the merger agreement and the analyses described below should not be viewed as determinative of the decision of the BOC board of directors with respect to the fairness of the merger consideration.

Piper Sandler reviewed the financial terms of the proposed merger. Pursuant to the terms of the merger agreement, at the effective time, each share of PMB common stock and non-voting common stock issued and outstanding immediately prior to the effective time, except for certain shares of PMB common stock as specified in the merger agreement, shall be converted into the right to receive 0.5 of a share of common stock of BOC.

Piper Sandler calculated an aggregate implied transaction value of approximately $245.5 million consisting of the implied value of 23,592,138 shares of PMB common stock outstanding, 574,587 PMB options outstanding with a weighted average strike price of $7.08, 75,000 restricted stock units, and 194,247 unvested restricted stock awards, based on an implied purchase price per share of $10.22, the closing price of BOC common stock on March 18, 2021. Based upon financial information for PMB as of or for the last twelve months (“LTM”) ended December 31, 2020 and the closing price of PMB’s common stock on March 18, 2021, Piper Sandler calculated the following implied transaction metrics:

Piper Sandler reviewed the publicly available historical reported trading prices of BOC common stock and PMB common stock for the one-year and three-year periods ended March 18, 2021. Piper Sandler then compared the relationship between the movements in the price of BOC common stock and PMB common stock, respectively, to movements in their respective peer groups⁴ (each as described below) as well as certain stock indices.

Piper Sandler used publicly available information to compare selected financial information for BOC with a group of financial institutions selected by Piper Sandler. The BOC peer group included nationwide major exchange-traded (NASDAQ and NYSE) banks and thrifts with total assets between $6.5 billion and $10.0 billion and LTM net income as a percentage of average assets between 0.00% to 0.75%, but excluded targets of announced merger transactions (the “BOC Peer Group”). The BOC Peer Group consisted of the following companies:

The analysis compared publicly available financial information for BOC with corresponding data for the BOC Peer Group as of or for the year ended December 31, 2020 (unless otherwise noted) with pricing data as of March 18, 2021. The table below sets forth the financial information for BOC and the median, mean, low and high data for the BOC Peer Group.

Piper Sandler used publicly available information to perform a similar analysis for PMB by comparing selected financial information for PMB with a group of financial institutions selected by Piper Sandler. The PMB peer group included publicly-traded (NASDAQ, NYSE, and OTC) banks and thrifts headquartered in California with total assets between $1.0 billion and $2.5 billion, but excluded (1) targets of announced merger transactions and (2) companies traded on the OTC Pink Open Market (the “PMB Peer Group”). The PMB Peer Group consisted of the following companies:

The analysis compared publicly available financial information for PMB with corresponding data for the PMB Peer Group as of or for the year ended December 31, 2020 (unless otherwise noted) with pricing data as of March 18, 2021. The table below sets forth the financial information for PMB and the median, mean, low and high data for the PMB Peer Group.

Piper Sandler reviewed recent merger and acquisition transactions. The group consisted of nationwide bank and thrift transactions announced between January 1, 2020 and March 18, 2021 with target assets between $1.0 billion and $2.5 billion (the “Nationwide Precedent Transactions”).

The Nationwide Precedent Transactions group was composed of the following transactions:

Using the latest publicly available information prior to the announcement of the relevant transaction, Piper Sandler reviewed the following transaction metrics: transaction price to last-twelve-months earnings per share, transaction price to estimated earnings per share, transaction price to tangible book value per share, core deposit premium, and 1-day market premium. Piper Sandler compared the indicated transaction metrics for the merger to the median, mean, low and high metrics of the Nationwide Precedent Transactions group.

Piper Sandler performed an analysis that estimated the net present value of BOC common stock assuming BOC performed in accordance with publicly available mean analyst earnings per share estimates for BOC for the years ending December 31, 2021 and December 31, 2022 with an estimated long-term annual asset and earnings per share growth rate for BOC for the years ending December 31, 2023, December 31, 2024 and December 31, 2025, as well as estimated dividends per share for BOC for the years ending December 31, 2021 through December 31, 2025, as provided by the senior management of BOC. To approximate the terminal value of a share of BOC common stock at December 31, 2025, Piper Sandler applied price to 2025 earnings per share multiples ranging from 15.0x to 25.0x and price to 2025 tangible book value per share multiples ranging from 120% to 170%. The terminal values were then discounted to present values using different discount rates ranging from 9.0% to 15.0%, which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of BOC common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of BOC common stock of $12.28 to $25.57 when applying multiples of earnings and $12.38 to $22.07 when applying multiples of tangible book value.

Piper Sandler also considered and discussed with the BOC board of directors how this analysis would be affected by changes in the underlying assumptions, including variations with respect to earnings. To illustrate this impact, Piper Sandler performed a similar analysis, assuming BOC’s earnings varied from 15.0% above estimates to 15% below estimates. This analysis resulted in the following range of per share values for BOC’s common stock, applying the price to 2025 earnings multiples range of 15.0x to 25.0x referred to above and a discount rate of 13.43%.

Piper Sandler also performed an analysis that estimated the net present value per share of PMB common stock, assuming PMB performed in accordance with publicly available mean analyst net income estimates for PMB for the years ending December 31, 2021 and December 31, 2022, as well as an estimated long-term annual asset and earnings per share growth rate for the years ending December 31, 2023, December 31, 2024 and December 31, 2025 and estimated dividends per share for PMB for the years ending December 31, 2021 through December 31, 2025, as provided by the senior management of BOC. To approximate the terminal value of a share of PMB common stock at December 31, 2025, Piper Sandler applied price to 2025 earnings per share multiples ranging from 10.0x to 20.0x and price to 2025 tangible book value per share multiples ranging from 95% to 135%. The terminal values were then discounted to present values using different discount rates ranging from 11.5% to 14.5%, which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of PMB common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of PMB common stock of $3.87 to $8.78 when applying multiples of earnings and $5.04 to $8.13 when applying multiples of tangible book value.

Piper Sandler also considered and discussed with the BOC board of directors how this analysis would be affected by changes in the underlying assumptions, including variations with respect to earnings. To illustrate this impact, Piper Sandler performed a similar analysis assuming PMB’s earnings varied from 15.0% above estimates to 15.0% below estimates. This analysis resulted in the following range of per share values for PMB common stock, applying the price to 2025 earnings multiples range of 10.0x to 20.0x referred to above and a discount rate of 13.31%.

Piper Sandler also performed an analysis that estimated the net present value per share of PMB common stock, assuming (a) PMB performed in accordance with publicly available mean analyst net income estimates for PMB for the years ending December 31, 2021 and December 31, 2022, and (b) an estimated long-term annual asset and earnings per share growth rate for the years ending December 31, 2023, December 31, 2024 and December 31, 2025 and estimated dividends per share for PMB for the years ending December 31, 2021 through December 31, 2025, and cost savings of 35% of PMB’s projected noninterest expense and $18.2 million of pre-tax transaction expenses associated with achieving such cost savings, as provided by the senior management of BOC. To approximate the terminal value of a share of PMB common stock at December 31, 2025, Piper Sandler applied price to 2025 earnings multiples ranging from 10.0x to 20.0x and multiples of 2025 tangible book value ranging from 95% to 135%. The terminal values were then discounted to present values using different discount rates ranging from 11.5% to 14.5%, which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of PMB common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of PMB common stock of $6.40 to $14.51 when applying multiples of earnings and $5.67 to $9.14 when applying multiples of tangible book value.