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): May 7, 2026

Advanced Energy Industries, Inc.

(Exact name of registrant as specified in its charter)

(970) 407-6626

(Registrant’s telephone number, including area code)

Not applicable

(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 (see General Instruction A.2. below):

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 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

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 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Amendment and restatement of the Amended and Restated 2023 Omnibus Incentive Plan

As described below under Item 5.07 of this Current Report on Form 8-K, at the 2026 Annual Meeting of Stockholders of Advanced Energy Industries, Inc. (the “Company”) held on May 7, 2026 (the “Annual Meeting”), the Company’s stockholders approved an amendment and restatement of the Company’s Amended and Restated 2023 Omnibus Incentive Plan (as amended and restated, the “Second Amended and Restated 2023 Plan”), which increases the total number of shares of common stock authorized for issuance thereunder from 2,400,000 shares to 4,900,000 shares and extends the termination date of the Second Amended and Restated 2023 Plan from April 27, 2033 to May 7, 2036.

The Second Amended and Restated 2023 Plan is described in detail in Proposal 5 in the Company's Definitive Proxy Statement on Schedule 14A filed with the U.S. Securities and Exchange Commission on March 26, 2026 (the “Proxy Statement”), and the full text of the Second Amended and Restated 2023 Plan is attached to the Proxy Statement as Appendix C. The description of the amendment and restatement of the Second Amended and Restated 2023 Plan set forth above is a summary only and is qualified in its entirety by reference to the full text of the Second Amended and Restated 2023 Plan, which is filed as Exhibit 10.1 to this Current Report on Form 8-K and incorporated herein by reference.

Item 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

As described in Item 5.02 above, the Company held its Annual Meeting on May 7, 2026. At the Annual Meeting, the Company's stockholders approved an amendment to the Company's existing Amended and Restated Certificate of Incorporation. As further disclosed in Proposal 4 of the Proxy Statement, the amendment increases the number of authorized shares of common stock from 70,000,000 shares to 140,000,000 shares.

The amendment became effective upon the filing of a Certificate of Amendment to the Amended and Restated Certificate of Incorporation (the “Certificate of Amendment”) with the Secretary of State of the State of Delaware on May 7, 2026. The foregoing summary of the amendment to the Amended and Restated Certificate of Incorporation does not purport to be complete and is qualified in its entirety by reference to the Certificate of Amendment.

A copy of the Certificate of Amendment as filed with the Secretary of State of the State of Delaware on May 7, 2026 is attached as Exhibit 3.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 5.07 Submission of Matters to a Vote of Security Holders

As described in Item 5.02 above, the Company held its Annual Meeting on May 7, 2026 to vote on five proposals. The following matters as set forth in the Proxy Statement were voted upon with the results indicated below.

The following ten nominees were elected to serve as directors of the Company, with the following votes tabulated:

Each director has been elected to serve until the 2027 Annual Meeting of Stockholders, or until his or her successor has been elected and qualified or until such director’s earlier resignation or removal.

The appointment of Ernst & Young LLP as the Company’s independent registered public accounting firm for 2026 was ratified, with the following votes tabulated:

The advisory approval of the compensation of the Company’s named executive officers as disclosed in the Proxy Statement was approved, with the following votes tabulated:

The amendment to the Amended and Restated Certificate of Incorporation was approved, with the following votes tabulated:

The amendment and restatement of the Amended and Restated 2023 Omnibus Incentive Plan was approved, with the following votes tabulated:

Item 9.01 Financial Statements and Exhibits.

(d) 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 hereunto duly authorized.