Ultra Clean Holdings, Inc.

Item 1.01. Entry into a Material Definitive Agreement. Sales Agreement On August 14, 2026, Ultra Clean Holdings, Inc. (the “Company”) entered into a sales agreement (the “Sales Agreement”) with UBS Securities LLC, Barclays Capital Inc., Craig-Hallum Capital Group LLC and Oppenheimer & Co. Inc. (each, a “Sales Agent” and collectively, the “Sales Agents”), under which the Company may offer and sell, from time to time in its sole discretion, up to $400 million of shares of its common stock, $0.001 par value per share (the “Common Stock”), through an “at-the-market” offering program (the “ATM Offering”). Subject to the terms and conditions of the Sales Agreement, the Sales Agents will use reasonable efforts consistent with their normal trading and sales practices, applicable state and federal laws, rules and regulations, and the rules of The Nasdaq Global Select Market to sell the shares of Common Stock from time to time based upon the Company’s instructions for the sales, including any price, time or size limits specified by the Company. Under the Sales Agreement, the Sales Agents may sell the shares of Common Stock by any method permitted by law, including in ordinary brokers’ transactions, to or through a market maker, on or through The Nasdaq Global Select Market or any other market venue where the securities may be traded, in the over-the-counter market, in privately negotiated transactions, or through a combination of any such methods of sale. The Company is not obligated to sell any shares of Common Stock under the Sales Agreement and may at any time suspend sales under the Sales Agreement. The Sales Agents’ obligations to sell the shares of Common Stock under the Sales Agreement are subject to satisfaction of certain conditions, including customary closing conditions. The Sales Agreement provides that the Sales Agents will be entitled to compensation for their services in the form of a commission of up to 3.0% of the gross offering proceeds of shares of Common Stock sold under the Sales Agreement, and the Company has agreed to reimburse the Sales Agents for certain specified expenses. The Company has also agreed to provide the Sales Agents with customary indemnification and contribution rights. The Sales Agreement may be terminated for any reason by the Company at any time by giving written notice to the Sales Agents or by any Sales Agent at any time, with respect to such Sales Agent only, by giving written notice to the Company. The sales and issuances of the shares of Common Stock under the Sales Agreement will be made pursuant to an automatic shelf registration statement on Form S-3 initially filed with the Securities and Exchange Commission (the “SEC”) on March 25, 2024 (Registration No. 333-278195) (the “Shelf Registration Statement”), a base prospectus, dated March 25, 2024, included as part of the Shelf Registration Statement and a prospectus supplement, dated August 14, 2026. The foregoing description of the Sales Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Sales Agreement, a copy of which is filed herewith as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated herein by reference. A validity opinion issued by the Company’s counsel with respect to the shares of Common Stock sold in the ATM Offering is filed as Exhibit 5.1 hereto. This Current Report on Form 8-K shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of such securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.