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): September 14, 2016

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (781) 622-1000

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 September 14, 2016, Thermo Fisher Scientific Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with J.P. Morgan Securities LLC, Citigroup Global Markets Inc. and Deutsche Bank Securities Inc., as representatives of the several underwriters named in Schedule A thereto, for the issuance and sale by the Company of $1,200,000,000 aggregate principal amount of its 2.950% Senior Notes due 2026 (the “Notes”) in a public offering pursuant to a registration statement on Form S-3, as amended by the Post-Effective Amendment No.1 thereto (File No. 333-209867), and a related preliminary prospectus supplement filed with the Securities and Exchange Commission on September 14, 2016.

The Company expects that the net proceeds from the sale of the Notes will be approximately $1.18 billion after deducting the underwriting discount and estimated offering expenses. The Company intends to use a portion of the net proceeds of the offering to redeem all of the outstanding $900 million aggregate principal amount of the Company’s 1.30% senior notes due 2017, which mature on February 1, 2017. The Company intends to use the remaining net proceeds for general corporate purposes, which may include, without limitation, the repayment, redemption or refinancing of indebtedness, capital expenditures, funding of possible acquisitions, working capital, satisfaction of other obligations or the repurchase of its outstanding equity securities.

The Notes will be issued pursuant to an indenture, dated as of November 20, 2009, between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”), as supplemented by the Fourteenth Supplemental Indenture, to be dated as of September 19, 2016, between the Company and the Trustee.

The above description of the Underwriting Agreement is qualified in its entirety by reference to the Underwriting Agreement, which is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

See Exhibit Index attached hereto.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EXHIBIT INDEX