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): June 29, 2016

SOUTHWESTERN ENERGY COMPANY

(Exact name of registrant as specified in its charter)

10000 Energy Drive

Spring, Texas 77389

(Address of principal executive office) (Zip Code)

(832) 796-1000

(Registrants’ telephone number, including area code)

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:

Common Stock

On June 29, 2016, Southwestern Energy Company (the “Company”) entered into an Underwriting Agreement, dated June 29, 2016 (the “Underwriting Agreement”) between the Company and Credit Suisse Securities (USA) LLC as representative of the underwriters named therein (the “Underwriters”), with respect to the offer and sale of 98,900,000 shares of the Company’s common stock, par value $0.01 per share (the “Common Stock”). The securities sold pursuant to the Underwriting Agreement were registered under the Company’s registration statement on Form S-3 (File No. 333-208074). The closing of the sale of Common Stock occurred on July 5, 2016.

The Underwriting Agreement sets forth the public offering price of $13.00 per share of Common Stock, and provides, among other things, that the Underwriters will purchase the Common Stock from the Company at the public offering price, less a discount of $0.38 per share.

Underwriting Agreement

The Underwriting Agreement includes customary representations, warranties and covenants by the Company. It also provides for customary indemnification by each of the Company and the Underwriters party thereto against certain liabilities arising out of or in connection with sale of the Common Stock and for customary contribution provisions in respect of those liabilities.

The Underwriters and their affiliates have provided, and in the future may continue to provide, various financial advisory, cash management, investment banking, commercial banking and other financial services, including the provision of credit facilities, to the Company in the ordinary course of business for which they have received and will continue to receive customary compensation.

The foregoing summary of the material terms of the Underwriting Agreement and the transactions contemplated thereby is subject to, and qualified in its entirety by, the full text of the Underwriting Agreement, which is attached hereto as Exhibit 1.1 and incorporated herein by reference.

The Underwriting Agreement has been filed with this Current Report on Form 8-K to provide investors and security holders with information regarding its terms. It is not intended to provide any other factual information about the Company. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties. The representations and warranties may have been made for the purposes of allocating contractual risk between the parties to the agreement instead of establishing these matters as facts, and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to investors. Investors are not third-party beneficiaries under the Underwriting Agreement and should not rely on the representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of the Company or any of its subsidiaries or affiliates. Moreover, information concerning the subject matter of the representations and warranties may change after the date of the Underwriting Agreement, which subsequent information may or may not be fully reflected in the Company’s public disclosures.

The information in this Item 7.01, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Exchange Act or otherwise subject to the liabilities of Section 18, and shall not be incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, except as set forth by specific reference in such filing.

On July 5, 2016, the Company issued a press release announcing the closing of its Common Stock offering, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

EXHIBIT INDEX

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.

EXHIBIT INDEX

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