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): February 10, 2017

Power Solutions International, Inc.

(Exact name of registrant as specified in its charter)

201 Mittel Drive, Wood Dale, Illinois 60191

(Address of principal executive offices and zip code)

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 (see General Instruction A.2. below):

On February 10, 2017, the Board of Directors of Power Solutions International, Inc. (the “Company”) appointed Frazier & Deeter, LLC (“Frazier”) as the Company’s new independent registered public accounting firm effective February 10, 2017. The appointment of Frazier was recommended and approved by our Audit Committee of the Board of Directors (the “Audit Committee”).

During the two fiscal years ended December 31, 2015 and 2014 and the subsequent interim period through February 10, 2017, neither the Company, nor anyone on its behalf, consulted with Frazier regarding: (i) the application of accounting principles to a specified transaction, either completed or proposed; (ii) the type of audit opinion that might be rendered on the Company’s financial statements, and Frazier did not provide any written report or oral advice that Frazier concluded was an important factor considered by the Company in reaching a decision as to any such accounting, auditing or financial reporting issue; (iii) any matter that was the subject of a “disagreement” within the meaning of Item 304(a)(1)(iv) of Regulation S-K or (iv) any “reportable event” within the meaning of Item 304(a)(1)(v) of Regulation S-K other than the material weaknesses and the inability to rely on management representations identified by the Company’s former independent registered public accounting firm, RSM US LLP (“RSM”), in the Company’s Current Report on Form 8-K filed on February 3, 2017. The Audit Committee discussed the subject matter of these reportable events with RSM. The Company has authorized RSM to respond fully to all inquiries of Frazier concerning all matters related to the periods audited by RSM, including with respect to the subject matter of these reportable events.

Caution Regarding Forward-Looking Statements

This Form 8-K Current Report includes information that constitutes forward-looking statements. Forward-looking statements often address our expected future business and financial performance, and often contain words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” or “will.” By their nature, forward-looking statements address matters that are subject to risks and uncertainties. Any such forward-looking statements may involve risk and uncertainties that could cause actual results to differ materially from any future results encompassed within the forward-looking statements. Examples of such forward-looking statements include, but are not limited to, statements regarding potential impacts of Nasdaq’s notice, the ongoing nature of the Audit Committee’s internal review, and the ability to complete the restatement of the affected financial statements and address material weaknesses. Factors that could cause or contribute to such differences include: the final results of the Audit Committee’s internal review as it impacts the Company’s accounting, accounting policies and internal control over financial reporting; the reasons giving rise to the resignation of the Company’s prior independent registered public accounting firm; the time and effort required to complete the restatement of the affected financial statements and amend the related Form 10-K and Form 10-Q filings; the inability to obtain a hearing from the Hearing Panel and file delinquent periodic reports within the deadlines imposed by Nasdaq and the potential delisting of the Company’s common stock from Nasdaq; the subsequent discovery of additional adjustments to the Company’s previously issued financial statements; the timing of completion of necessary re-audits, interim reviews and audits by the new independent registered public accounting firm; the timing of completion of steps to address and the inability to address and remedy, material weaknesses; the identification of additional material weaknesses or significant deficiencies; risks relating to the substantial costs and diversion of personnel’s attention and resources deployed to address the financial reporting and internal control matters and related class action litigation; the impact of the resignation of the Company’s independent registered public accounting firm on the Company relationship with its lender and trade creditors and the potential for defaults and exercise of creditor remedies and the implications of the same for its strategic alternatives process; the potential delisting of the Company’s common stock from NASDAQ and any adverse effects resulting therefrom; and the impact of the previously disclosed investigation initiated by the SEC and any related or additional governmental investigative or enforcement proceedings. Actual events or results may differ materially from the Company’s expectations. The Company’s forward-looking statements are presented as of the date hereof. Except as required by law, the Company expressly disclaims any intention or obligation to revise or update any forward-looking statements, whether as a result of new information, future events or otherwise.

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.

Dated: February 10, 2017