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, 2013

NORTHWEST PIPE COMPANY

(Exact name of registrant as specified in its charter)

5721 SE Columbia Way, Suite 200

Vancouver, WA 98661

(360) 397-6250

(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:

On May 31, 2013, the Board of Directors of Northwest Pipe Company (the “Company”), upon the recommendation of the Compensation Committee, approved grants of restricted stock units (“RSUs”) and performance share awards (“PSAs”) for the following Executive Officers of the Company, as well as other senior members of management, in the amounts set forth below. Pursuant to these long-term incentive grants, each Executive Officer or other senior member of management received an award of RSUs and PSAs valued at an amount equal to a specific percentage of his or her respective annual base salary, with 25 percent of each award represented by RSUs and 75 percent of each award represented by PSAs. The RSUs awarded will vest ratably over a three year period based upon continued service with the Company. The PSAs awarded will vest on January 15, 2016 based on the Company’s total shareholder return for 2013 – 2015 as compared with a specified group of peer companies. The actual number of PSAs which will vest will be determined based on the performance level achieved and may be equal to, greater than, or less than the number of PSAs specified below. In the event of a “change in control” (as defined in the Agreements), vesting will be accelerated pro rata to reflect time elapsed and performance to date. The foregoing descriptions of the terms of the RSU and PSA awards are qualified by reference to the full text of the forms of Restricted Stock Unit Agreement and Performance Share Award Agreement (the “Agreements”), which are filed herewith as Exhibits 10.1 and 10.2 and incorporated herein by reference.

At the Northwest Pipe Company (the “Company”) Annual Meeting of Shareholders on May 31, 2013, the Company’s shareholders: (i) elected four directors; (ii) approved an Amendment to the Company’s 2007 Stock Incentive Plan to increase the number of shares authorized for issuance thereunder from 600,000 to 1,200,000; (iii) approved, on an advisory basis, the compensation paid to the Company’s named executive officers; and (iv) ratified the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accounting firm for the year ending December 31, 2013. Set forth below are the voting results for each of these proposals.

Proposal 1: Election of four directors:

Proposal 2: Vote on Amendment to the Company’s 2007 Stock Incentive Plan:

Proposal 3: Advisory vote on executive compensation:

Proposal 4: Ratification of the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accountants for the year ending December 31, 2013:

SIGNATURE

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 thereunto duly authorized on June 5, 2013.