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): February 25, 2026

Ultra Clean Holdings, Inc.

(Exact name of Registrant as Specified in Its Charter)

Registrant’s Telephone Number, Including Area Code: 510 576-4400

N/A

(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 8.01. Other Events.

Proposed Offering of Notes

On February 25, 2026, Ultra Clean Holdings, Inc. (the “Company”) issued a press release relating to its proposed offering of Convertible Senior Notes due 2031 (the “Notes”) to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference into this Item 8.01.

Anticipated Amendment to Credit Agreement

In connection with the pricing of the notes, the Company expects to enter into an amendment to the Credit Agreement dated as of August 27, 2018, by and among the Company, as parent borrower, Barclays Bank PLC, as administrative agent, and the lenders and other parties thereto from time to time, to modify the consolidated total gross leverage ratio financial maintenance covenant applicable only to the Company’s revolving credit facility thereunder. Such amendment would, among other things, increase such maximum consolidated total gross leverage ratio to 6.00 to 1.00 for a specified period of time on terms to be set forth in such amendment.

Neither this Current Report on Form 8-K nor the press release attached as Exhibit 99.1 to this Current Report on Form 8-K constitutes an offer to sell, or the solicitation of an offer to buy, the Notes or shares of the Company’s common stock, if any, issuable upon conversion of the Notes.

Item 9.01. Financial Statements and Exhibits.

Exhibits

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.