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 28, 2013

PFIZER INC.

(Exact name of registrant as specified in its charter)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 8.01 Other Events

On June 3, 2013, Pfizer Inc. (the “Company”) completed a public offering of $4,000,000,000 aggregate principal amount of notes comprised of $750,000,000 aggregate principal amount of its 0.900% Notes due 2017, $1,000,000,000 aggregate principal amount of its 1.500% Notes due 2018, $500,000,000 aggregate principal amount of its Floating Rate Notes due 2018, $1,000,000,000 aggregate principal amount of its 3.000% Notes due 2023 and $750,000,000 aggregate principal amount of its 4.300% Notes due 2043 (together, the “Notes”).

The offering of the Notes was made pursuant to the Company’s shelf registration statement on Form S-3 (Registration No. 333-181321) filed with the Securities and Exchange Commission on May 10, 2012.

In connection with the offering of the Notes, the Company entered into an underwriting agreement and related pricing agreement, each dated May 28, 2013, with Citigroup Global Markets Inc., Credit Suisse Securities (USA) LLC, Goldman, Sachs & Co. and RBS Securities Inc., as representatives of the several underwriters named therein.

The Notes were issued pursuant to an indenture, dated as of January 30, 2001, between the Company and The Bank of New York Mellon (formerly known as The Bank of New York), as successor to JPMorgan Chase Bank (formerly known as The Chase Manhattan Bank), as trustee, as supplemented by the third supplemental indenture, dated as of June 3, 2013, between the Company and The Bank of New York Mellon, as trustee.

The underwriting agreement, pricing agreement, indenture, third supplemental indenture (including forms of the Notes) and press release related to the offering are filed as exhibits to this Form 8-K and are incorporated herein by reference.

In addition, in connection with the offering of the Notes, the Company is filing a legal opinion regarding the validity of the Notes, attached as Exhibit 5.1 to this Form 8-K.

Item 9.01 Financial Statements and Exhibits

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SIGNATURE

Under the requirements of the Securities Exchange Act of 1934, the registrant has caused this report to be signed on its behalf by the authorized undersigned.

Dated: June 3, 2013

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EXHIBIT INDEX

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