8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 20, 2026

FIRST GUARANTY BANCSHARES, INC.

(Exact name of registrant as specified in its charter)

Check the appropriate box if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Securities registered pursuant to Section 12(b) of the Act:Title of each classTrading Symbol(s)Name of each exchange on which registeredCommon Stock, $1 par valueFGBIThe Nasdaq Stock Market LLCDepositary Shares (each representing a 1/40th interest in a share of 6.75% Series A Fixed-Rate Non-Cumulative perpetual preferred stock)FGBIPThe Nasdaq Stock Market LLC

Item 1.01 Entry into a Material Definitive Agreement

Second Amendment to Promissory Note

On March 20, 2026, First Guaranty Bancshares, Inc. (“First Guaranty” or the "Company”) entered into the Second Amendment to the Promissory Note (the “Second Promissory Note Amendment”) with Smith & Tate Investment, L.L.C. (“Smith & Tate), which further amends that certain Promissory Note, dated as of October 5, 2023, by and between First Guaranty and Smith & Tate, as successor to Burke & Herbert Bank & Trust Company, as successor to Summit Community Bank, Inc. (as amended, the “Promissory Note”). The Promissory Note was previously amended on June 4, 2025 (the "First Promissory Note Amendment"). Smith & Tate is a company controlled by Edgar Ray Smith, III, a director and principal shareholder of First Guaranty.

Prior to the First Promissory Note Amendment, the Promissory Note provided for the payment of thirty-nine (39) quarterly installments of principal in the amount of $1,007,812.50 (the “Principal Payments”) plus accrued but unpaid interest, beginning on December 31, 2023, and continuing on the last day of each consecutive calendar quarter thereafter, followed by a final payment on October 5, 2033, equal to the then-outstanding principal balance and all accrued but unpaid interest, penalties and fees due thereon. The First Promissory Note Amendment (a) waived Principal Payments beginning on the June 30, 2025, interest payment date and ending on the March 31, 2026, interest payment date (the “First Modified Payment Period”), and (b) allowed First Guaranty, at First Guaranty's option, to make payments of interest due during the First Promissory Note Modified Payment Period either (i) in cash, as provided for in the original Promissory Note, or (ii) in shares of common stock of First Guaranty, $1.00 par value (the “Common Stock”), with the number of shares of Common Stock to constitute each such interest payment equaling (x) the cash payment due as of such interest payment date based on the then-applicable interest rate as provided in the Promissory Note; divided by (y) the consolidated closing bid price per share of the Common Stock on the trading day immediately preceding the interest payment date.

The terms of the Second Promissory Note Amendment extend the waiver of Principal Payments beginning on the March 31, 2026, interest payment date and continuing through the March 31, 2028, interest payment date (the "Second Modified Payment Period") and also extend First Guaranty's ability to choose whether to make interest payments in cash or in the form of Common Stock during the Second Modified Payment Period.

The foregoing description of the Second Promissory Note Amendment does not purport to be complete and is qualified in its entirety by reference to the Second Promissory Note Amendment, which is filed as Exhibit 10.1 to this Current Report on Form 8-K.

Second Amendment to the Floating Rate Subordinated Note due March 28, 2034

On March 20, 2026, First Guaranty entered into the Second Amendment to the First Guaranty Bancshares, Inc. Floating Rate Subordinated Note due March 28, 2034 (the “Second Subordinated Note Amendment”) with Smith & Tate, which further amended that certain First Guaranty Bancshares, Inc. Floating Rate Subordinated Note due March 28, 2034 (the “Subordinated Note”). The Subordinated Note was previously amended on June 4, 2025 (the "First Subordinated Note Amendment"). As noted above, Smith & Tate is controlled by Edgar Ray Smith, III, a director and principal shareholder of the Company.

The Subordinated Note is for a ten-year term and bears interest at a floating rate based on the Prime Rate as reported by the Wall Street Journal plus 75 basis points for the period of time until redemption or maturity. The First Subordinated Note Amendment (a) changed the frequency of interest payments from monthly to quarterly and (b) during the First Modified Payment Period, allowed First Guaranty, at First Guaranty’s option, to make payments of interest either (i) in cash, as provided for in the original Subordinated Note, or (ii) in shares of Common Stock, with the number of shares of Common Stock to constitute each such interest payment equaling (x) the cash payment due as of such interest payment date based on the then-applicable interest rate as provided in the Subordinated Note; divided by (y) the consolidated closing bid price per share of the Common Stock on the trading day immediately preceding the interest payment date.

The terms of the Second Subordinated Note Amendment extend First Guaranty's ability to choose whether to make interest payments in cash or in the form of Common Stock during the Second Modified Payment Period.

The foregoing description of the Second Subordinated Note Amendment does not purport to be complete and is qualified in its entirety by reference to the Subordinated Note Amendment, which is attached as Exhibit 10.2 to this Current Report on Form 8-K.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

ex101secondamendmenttoth

SECOND AMENDMENT TO THE PROMISSORY NOTE This SECOND AMENDMENT TO THE PROMISSORY NOTE (this "Amendment") is made and entered into in respect of that certain Promissory Note, dated October 5, 2023 (the "Note"), by and between First Guaranty Bancshares, Inc. (the "Company") and Smith & Tate Investment,L.L.C. (the "Noteholder"), as successor to Burke & Herbert Bank & Trust Company, as successor to Summit Community Bank, Inc., as amended by the First Amendment to the Promissory Note, dated June 30, 2025, by and between the Company and the Noteholder (the "First Amendment"). WHEREAS, the terms of the Note provide for the payment of thirty-nine (39) quarterly installments of principal in the amount of One Million Seven Thousand and Eight Hundred Twelve Dollars and Fifty Cents ($1,007,812.50) (the "Principal Payment"), plus accrued interest through such date (each, an "Interest Payment"), beginning on December 37,2023 and continuing on the last day of each consecutive calendar quarter thereafter (each, a "Payment Date"), followed by a final payment on October 5,2033 equal to the then-outstanding principal balance and all accrued but unpaid interest, penalties and fees due thereon; WHEREAS, Section 8.5 of that certain Loan Agreement, dated as of October 5,2023 (lhe "Loan Agreement"), provides that any amendments or modifications to the Note must be in writing and signed by the Noteholder; and WHEREAS, the terms of the First Amendment provide for, among other things, modified Interest Payments beginning on the June 30, 2025, Payment Date and ending on the March 31, 2026, Payment Date; WHEREAS, the Company and the Noteholder have agreed to extend the duration of the modified Interest Payments and to certain other amendments and modifications to the Note. NOW, THEREFORE, in consideration of the foregoing, and the other promises, covenants and agreements set forth in this Amendment, the parties agree as follows: 1. Waiver of Principal Payment. The Noteholder agrees to waive payment of the Principal Payment for the nine (9) consecutive calendar quarters, beginning on the March 37,2026, Payment Date and ending on the March 31,2028, Payment Date (the "Modified Payment Period"), such that the next required Principal Payment on the Note as hereby amended shall be June 30, 2028. 2. Modification of Interest Payment. Each Interest Payment that becomes due and payable during the Modified Payment Period shall, at the Company's option, be made either (a) in cash as provided in the Note, or (b) in shares of common stock of the Company, $1.00 par value (the "Common Stock"), with the number of shares of Common Stock to constitute each such Interest Payment equaling (i) the cash payment due as of such Payment Date based on the then-applicable interest rate as provided in the Note; divided by (ii) the consolidated closing bid price per share on the trading day immediately preceding the Interest Page I of3

Payment Date. The Common Stock will be issued to the Noteholder's designee. The number of shares of Common Stock will be rounded down to the nearest whole share. 3. Effect of Amendment. Except as provided herein, all terms and conditions of the Note and the Loan Agreement will remain in full force and effect. This Amendment will not constitute an amendment or waiver of any provision of the Note not expressly amended by this Amendment' 4. Multiple Counterparts. For the convenience of the parties, this Amendment may be signed in multiple counterparts, each of which will be deemed an original, and all counterparts hereof so signed by the parties hereto, whether or not such counterpart will bear the execution of each of the parties hereto, will be deemed to be, and is to be construed as, one and the same Amendment. A facsimile or electronic scan in a ".pdf' format transmission of a signed counterpart of this Amendment will be sufficient to bind the party or parties whose signature(s) appear thereon. 5. Effectiveness. This Amendment will become effective upon the execution hereof by the Company and the Noteholder. 6. Miscellaneous. All capitalized terms used, but not otherwise defined herein, will have the meanings given to them in the Note. This Amendment will be binding upon and will inure to the benefit of the parties hereto, their respective legal representatives, successors in title, and assigns. In the event any provision of this Amendment is held to be invalid or unenforceable, such invalidity or unenforceability will not affect the validity or enforceability of any other provision hereof. [Signature Page FollowsJ Page 2 of 3

[Signature Page to AmendmentJ IN WITNESS WHEREOF, the Company has caused this Amendment to be executed as of the date first above written. FIRST GUARANTY BANCSHARES, INC. By: -/T{.i,t}raAQ @YL - Michael R. Mineer President and Chief Executive Officer IN WITNESS WHEREOF, the undersigned Noteholder has caused this Amendment to be executed as of the date first above written. SMITH & TATE INVESTMENTS, L.L.C Edgar Ray Smith III Member and Manager By Page 3 of3

ex102secondamendmenttoth

SECOND AMENDMENT TO THE FIRST GUARANTY BANCSHARES' INC. FLOATING RATE SUBORDINATED NOTE DUE MARCH28,2O34 ThiS SECOND AMENDMENT TO THE FIRST GUARANTY BANCSHARES, INC. FLOATING RATE SUBORDINATED NOTE DUE MARCH28,2034 (this "Amendment") is made and entered into in respect of that certain First Guaranty Bancshares, Inc. Floating Rate Subordinated Note due March 28, 2034 (the "subordinated Note"), issued by First Guaranty Bancshares, Inc. ("Company") to and currently held by Smith &Tate,Investments, L'L.C. (the 'oNoteholder"). All capitalized terms used, but not otherwise defined herein, will have the meanings given to them in the Subordinated Note. WHEREAS, Section 8.3 of that certain Subordinated Note Purchase Agreement, dated as of March 28,2024 (the "NPA"), by and between the Company and the Noteholder, provides the manner in which the Subordinated Note may be amended by the Company and the holders of the Subordinated Notes; WHEREAS, the Company and the Noteholder previously entered into that certain First Amendment to the First Guaranty Bancshares, Inc. Floating Rate Subordinated Note Due March 28,2034,which provided for, among other things, modified Interest Payments pursuant to Section 11 of the Subordinated Note; and WHEREAS, the Company and the Noteholder have agreed to certain amendments and modifications to the Subordinated Note. NOW, THEREFORE, in consideration of the foregoing, and the other promises, covenants and agreements set forth in this Amendment, the parties agree as follows: 1. Amendments to Subordinated Note. Section 1 1 of the Subordinated Note is hereby amended by replacing the reference to "June 30, 2025" with "March 31, 2026" and by replacing the reference to "March 3 1, 2026" to "March 31, 2028, such that the "Modified Payment Period" shall be from March3l,2026 through March 31,2028. 2. Effect of Amendment. Except as provided herein, all terms and conditions of the Subordinated Note will remain in full force and effect. This Amendment will not constitute an amendment or waiver of any provision of the Subordinated Note not expressly amended by this Amendment. 3. Multiple Counterparts. For the convenience of the parties, this Amendment may be signed in multiple counterparts, each of which will be deemed an original, and all counterparts hereof so signed by the parties hereto, whether or not such counterpart will bear the execution of each of the parties hereto, will be deemed to be, and is to be construed as, one and the same Amendment. A facsimile or electronic scan in a ".pdf'format transmission of a signed counterpart of this Amendment will be sufficient to bind the party or parties whose signature(s) appear thereon. 4. Effectiveness. This Amendment will become effective upon the execution hereof by the Company and the Noteholder. Page 1 of3

5. Miscellaneous. This Amendment will be binding upon and will inure to the benefit of the parties hereq their respective legal representatives, successors in title, and assigns. In the event any provision of this Amendment is held to be invalid or unenforceable, such invalidity or unenforceability will not affect the validity or enforceability of any other provision hereof. [Signature Page FollowsJ Page2 of3

[Signature Page to AmendmentJ IN WITNESS WHEREOF, the Company has caused this Amendment to be executed as of the date first above written. FIRST GUARANTY BANCSHARES, INC. Michael R. Mineer President and Chief Executive Officer IN WITNESS WHEREOF, the undersigned Noteholder has caused this Amendment to be executed as of the date first above written. SMITH & TATE INVESTMENTS, L.L.C By: Smith III Member and Manager By