As filed with the Securities and Exchange Commission on June 25, 2013

Registration No. 333-187472

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 3

TO

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

CDW CORPORATION

(Exact name of registrant as specified in its charter)

200 N. Milwaukee Avenue

Vernon Hills, Illinois 60061

Telephone: (847) 465-6000

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Christine A. Leahy

Senior Vice President, General Counsel and Corporate Secretary

CDW Corporation

200 N. Milwaukee Avenue

Vernon Hills, Illinois 60061

Telephone: (847) 465-6000

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale of the securities to the public:

As soon as practicable after this Registration Statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box: ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” accelerated filer,” and “smaller reporting company” in Rule 12b-2 of the Exchange Act (Check one):

CALCULATION OF REGISTRATION FEE

The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

This Amendment No. 3 to the Registration Statement on Form S-1 (File No. 333-187472) is being filed solely for the purpose of filing Exhibits 1.1 and 4.1. No change is made to the prospectus constituting Part I of the Registration Statement (and, accordingly, a preliminary prospectus has been omitted) or Items 13, 14, 15 and 17 of Part II of the Registration Statement.

Part II: Information not required in the prospectus

Item 13. Other expenses of issuance and distribution.

The following table sets forth the various expenses, other than underwriting discounts and commissions, payable by us in connection with the sale of the common stock being registered. All of the amounts shown are estimated, except the Securities and Exchange Commission registration fee and FINRA filing fee.

Item 14. Indemnification of directors and officers.

Section 145 (“Section 145”) of the Delaware General Corporation Law, as the same exists or may hereafter be amended (the “DGCL”), provides that a Delaware corporation may indemnify any persons who were, are or are threatened to be made, parties to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person is or was an officer, director, employee or agent of such corporation, or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided such person acted in good faith and in a manner he reasonably believed to be in or not opposed to the corporation’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe that his conduct was illegal. A Delaware corporation may indemnify any persons who are, were or are threatened to be made, a party to any threatened, pending or completed action or suit by or in the right of the corporation by reasons of the fact that such person was a director, officer, employee or agent of such corporation, or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit, provided such person acted in good faith and in a manner he reasonably believed to be in or not opposed to the corporation’s best interests, provided that no indemnification is permitted without judicial approval if the officer, director, employee or agent is adjudged to be liable to the corporation. Where an officer, director, employee or agent is successful on the merits or otherwise in the defense of any action referred to above, the corporation must indemnify him against the expenses which such officer or director has actually and reasonably incurred.

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Section 145 further authorizes a corporation to purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or enterprise, against any liability asserted against him and incurred by him in any such capacity, arising out of his status as such, whether or not the corporation would otherwise have the power to indemnify him under Section 145.

Our amended and restated certificate of incorporation limits, to the maximum extent permitted by Delaware law, the personal liability of directors for monetary damages for breach of their fiduciary duties as a director. Our amended and restated bylaws provide that directors, officers and employees will be indemnified to the fullest extent authorized by the DGCL with respect to actions, suits or proceedings. Our amended and restated bylaws require us to pay all expenses incurred by a director, officer or employee in defending any such proceeding.

We currently have directors’ and officers’ liability insurance policies to insure our directors and officers against liability for actions or omissions occurring in their capacity as a director or officer, subject to certain exclusions or limitations. Reference is made to the form of underwriting agreement filed as Exhibit 1.1 hereto for provisions providing that the underwriters are obligated, under certain circumstances, to indemnify our directors, officers and controlling persons against certain liabilities under the Securities Act. There is currently no pending material litigation or proceeding involving any of our directors, officers or employees for which indemnification is sought.

Prior to the completion of this offering, we will also enter into indemnification agreements with each of our executive officers and directors. The indemnification agreements will provide the executive officers and directors with contractual rights to indemnification, expense advancement and reimbursement, to the fullest extent permitted under Delaware law.

Item 15. Recent sales of unregistered securities.

None.

Item 16. Exhibits and financial statement schedules.

Exhibits.

The attached Exhibit Index is incorporated herein by reference.

Financial statement schedules.

The following financial statement schedule is included at page F-60 of Amendment No. 2 to Registration Statement on Form S-1 filed on June 14, 2013 (Reg. No. 333-187472):

All other schedules for which provision is made in the applicable accounting regulations of the SEC are not required under the related instructions, are inapplicable or not material, or the information called for thereby is otherwise included in the financial statements and therefore has been omitted.

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Item 17. Undertakings.

(a) The undersigned registrant hereby undertakes to provide to the underwriters at the closing specified in the underwriting agreement certificates in such denominations and registered in such names as required by the underwriters to permit prompt delivery to each purchaser.

(b) Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended, may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction, the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

(c) The undersigned registrant hereby further undertakes that:

(1) For purposes of determining any liability under the Securities Act of 1933, as amended, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

(2) For the purpose of determining any liability under the Securities Act of 1933, as amended, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) For the purpose of determining liability of the registrant under the Securities Act of 1933, as amended, to any purchaser, each prospectus filed pursuant to Rule 424(b) as part of a registration statement relating to an offering, other than registration statements relying on Rule 430B or other than prospectuses filed in reliance on Rule 430A, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such date of first use.

(4) That, for the purpose of determining liability of the registrant under the Securities Act of 1933, as amended, to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will

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be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

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Signatures

Pursuant to the requirements of the Securities Act of 1933, CDW Corporation, a Delaware corporation, has duly caused this Amendment No. 3 to Registration Statement on Form S-1 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Vernon Hills, State of Illinois, on June 25, 2013.

Pursuant to the requirements of the Securities Act of 1933, this Amendment No. 3 to Registration Statement on Form S-1 has been signed by the following persons in the capacities indicated on June 25, 2013.

Exhibit index