8-K

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

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

Ultra Clean Holdings, Inc.

(Exact name of Registrant as Specified in Its Charter)

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the 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))

Securities registered pursuant to Section 12(b) of the Act:

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. ☐

Item 5.07 Submission of Matters to a Vote of Security Holders.

On May 22, 2026, at the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Ultra Clean Holdings, Inc. (the “Company”), the stockholders of the Company considered and approved three proposals, each of which is described in more detail in the Company’s definitive proxy statement for the Annual Meeting filed with the Securities and Exchange Commission on April 27, 2026.

The vote results detailed below represent the final results as certified by the Inspector of Elections:

Proposal 1

Election of directors for a one-year term.

Proposal 2

Ratification of the appointment of PricewaterhouseCoopers LLP to serve as the Company’s independent registered public accounting firm for fiscal 2026.

Proposal 3

Approval, by non-binding advisory vote, of the compensation paid by the Company to its Named Executive Officers.

Proposal 4

Approval of the amendment and restatement of the Company’s stock incentive plan (the “Plan”) to increase the number of shares available for issuance under the Plan by an additional 3,500,000 shares.

Proposal 5

Approval of the amendment and restatement of the Company’s employee stock purchase plan (the “ESPP”) to increase the number of shares available for issuance under the ESPP by an additional 450,000 shares.

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 thereunto duly authorized.