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 12, 2012

POWER SOLUTIONS INTERNATIONAL, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (630) 350-9400

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:

On November 12, 2012, we announced our results of operations and financial position, as of and for the three- and nine-month period ended September 30, 2012. The press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference. A transcript of the conference call discussing our results of operations and financial condition, as of and for the three- and nine-month period ended September 30, 2012, which also took place on November 12, 2012, is attached hereto as Exhibit 99.2 and is incorporated herein by reference.

Cautionary Note Regarding Forward-Looking Statements

This Current Report on Form 8-K, including the exhibits hereto, contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, including statements regarding the current expectations of Power Solutions International, Inc. (the “Company”) about its prospects and opportunities, including expectations for the Company’s expanded manufacturing facilities. The Company has tried to identify these forward looking statements by using words such as “expect,” “anticipate,” “estimate,” “plan,” “will,” “would,” “should,” “forecast,” “believe,” “guidance,” “projection” or similar expressions, but these words are not the exclusive means for identifying such statements. The Company cautions that a number of risks, uncertainties and other important factors could cause the Company’s actual results to differ materially from those expressed in, or implied by, the forward-looking statements, including, without limitation, the development of the market for alternative fuel power systems, technological and other risks relating to the Company’s development of its new 8.8 liter engine, introduction of other new products and entry into on-road markets (including the risk that these initiatives may not be successful), the significant strain on our senior management team, support teams, manufacturing lines, information technology platforms and other resources resulting from rapid expansion of our operations, changes in environmental and regulatory policies, significant competition, general economic conditions and the Company’s dependence on key suppliers. For a detailed discussion of factors that could affect the Company’s future operating results, please see the Company’s SEC filings, including the disclosures under “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in those filings. Except as expressly required by the federal securities laws, the Company undertakes no obligation to update or revise any forward-looking statements, whether as a result of new information, changed circumstances or future events or for any other reason.

The information in this Form 8-K (including the exhibits hereto) shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

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.