Table of Contents

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

March 11, 2013

Date of Report

(Date of earliest event reported: March 5, 2013)

HARMONIC INC.

(Exact name of Registrant as specified in its charter)

4300 North First Street

San Jose, CA 95134

(408) 542-2500

(Address, including zip code, and telephone number, including area code, of Registrant’s principal executive offices)

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):

Table of Contents

TABLE OF CONTENTS

2

Table of Contents

Item 2.01 Completion of Acquisition or Disposition of Assets

On February 18, 2013, Harmonic Inc. (“Harmonic” or the “Company”) entered into an Asset Purchase Agreement (the “Purchase Agreement”) with Aurora Networks, Inc. (“Aurora”), pursuant to which Aurora would acquire the cable access HFC business of Harmonic (the “Transaction”).

On March 5, 2013, the Company completed the Transaction and received gross proceeds of $46 million in cash, as provided in the Purchase Agreement.

The foregoing description of the Purchase Agreement does not purport to be complete and is qualified in its entirety by reference to the Purchase Agreement, a copy of which is filed as Exhibit 2.1 to this Form 8-K and is incorporated by reference herein.

Item 8.01 Other Event

On March 6, 2013, the Company issued a press release announcing the completion of the Transaction, a copy of which is filed as Exhibit 99.1 to this Form 8-K and is incorporated by reference herein.

Item 9.01 Financial Statements and Exhibits

(b) Pro Forma Financial Information.

The unaudited pro forma condensed consolidated balance sheet of the Company as of December 31, 2012 and unaudited pro forma condensed consolidated statements of operations of the Company for the fiscal years ended December 31, 2012, December 31, 2011 and December 31, 2010, in each case giving effect to the Transaction, are filed as Exhibit 99.2 to this Form 8-K and are incorporated by reference herein.

(d) Exhibits.

3

Table of Contents

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.

4

Table of Contents

EXHIBIT INDEX

5

Table of Contents

6