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 31, 2017

Acacia Communications, Inc.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (978) 938-4896

(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:

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.  ☒

On May 31, 2017, Acacia Communications, Inc. (the “Company”) announced that it has identified a quality issue that it currently believes affects a portion of the approximate 1,300 AC400 units and 5,000 CFP units manufactured by one of its three contract manufacturers over an approximate four month period. The Company believes the root cause of this quality issue has been identified as a circuit board cleaning process that has since been eliminated, and manufacturing at this contract manufacturer has resumed. The Company does not believe that products currently being shipped are affected by this quality issue. The Company is actively working with affected customers to remediate this issue. The Company is also working to estimate the cost of these remediation efforts and assess the impact of this issue on its near-term manufacturing capacity. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99. 1 to this Current Report on Form 8-K.

Cautionary Note Regarding Forward-Looking Statements

This Current Report on Form 8-K includes statements concerning the Company and its future expectations, plans and prospects that constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. For this purpose, any statements contained herein that are not statements of historical fact may be deemed to be forward-looking statements. Without limiting the foregoing, the words “may,” “should,” “expects,” “plans,” “anticipates,” “could,” “intends,” “target,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions are intended to identify forward-looking statements. The Company has based these forward-looking statements largely on its current expectations and projections about future events and financial trends that the Company believes may affect its business, financial condition and results of operations. These forward-looking statements speak only as of the date of this Current Report on Form 8-K and are subject to a number of risks, uncertainties and assumptions including, without limitation, the Company’s anticipated growth strategies, its expectations regarding competition, the anticipated trends and challenges in its business and the market in which the Company operates, including those that may affect its customers and their demand for the Company’s products, its expectations regarding, and the stability of, its supply chain and manufacturing, the scope, progress, expansion and costs of developing and commercializing its products, the size and growth of the potential markets for its products and the ability to serve those markets, regulatory developments in the United States and foreign countries, including under export control laws or regulations that could impede its ability to sell its products to customers in certain foreign jurisdictions, and other risks set forth under the caption “Risk Factors” in the Company’s public reports filed with the SEC, including the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 and its Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2017 filed with the SEC. The Company assumes no obligation to update any forward-looking statements contained in this Current Report on Form 8-K as a result of new information, future events or otherwise.

The information in this Item 7.01 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended. The information contained in this Item 7.01 shall not be incorporated by reference into any filing with the SEC made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing.

(d) Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EXHIBIT INDEX