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): December 2, 2014

CDW CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (847) 465-6000

None

(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:

On December 2, 2014, CDW Corporation (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Barclays Capital Inc. as the representative of the several underwriters listed on Schedule 1 thereto (the “Underwriters”) and the selling stockholders listed on Schedule 2 thereto (the “Selling Stockholders”) with respect to an underwritten public offering of 17,250,000 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”), which amount includes the Underwriters’ option to purchase up to an additional 2,250,000 shares of Common Stock (the “Option Shares”), at a public offering price of $33.28 per share, to be sold by the Selling Stockholders. On December 4, 2014, the Underwriters exercised their option to purchase all of the 2,250,000 Option Shares. The closing of the offering and delivery of the Shares took place on December 8, 2014. The Company did not receive any proceeds from the sale of the Shares.

The offering was made pursuant to (i) an effective Registration Statement on Form S-3ASR (the “Registration Statement”) filed with the Securities and Exchange Commission (the “SEC”) on October 16, 2014 (File No. 333-199425), including a related base prospectus dated October 16, 2014, and (ii) a related prospectus supplement dated December 2, 2014 and filed with the SEC on December 4, 2014 pursuant to Rule 424(b)(7) under the Securities Act of 1933, as amended.

The Underwriting Agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K, and is incorporated by reference in the Registration Statement. The description of the Underwriting Agreement in this report is a summary and is qualified in its entirety by the terms of the Underwriting Agreement.

(d) Exhibits

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.

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