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): November 3, 2025

HARMONIC INC.

(Exact name of Registrant as specified in its charter)

2590 Orchard Parkway

San Jose, CA 95131

(Address of principal executive offices, including zip code)

(408) 542-2500

(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:

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 2.02. Results of Operations and Financial Condition.

On November 3, 2025, Harmonic Inc. ("Harmonic" or the “Company”) issued a press release regarding its preliminary unaudited financial results for the quarter ended September 26, 2025. In the press release, Harmonic also announced that it would be holding a conference call on November 3, 2025 to discuss its financial results for the quarter ended September 26, 2025. A copy of the press release is furnished as Exhibit 99.1 hereto, and the information in Exhibit 99.1 is incorporated herein by reference.

The information in this Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that Section, and this Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 furnished herewith shall not be incorporated by reference into any filing by Harmonic under the Securities Act of 1933, as amended (the “Securities Act”), or under the Exchange Act.

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.