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): April 30, 2015

FS Investment Corporation

(Exact name of Registrant as specified in its charter)

Registrant’s telephone number, including area code: (215) 495-1150

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 April 30, 2015, FS Investment Corporation (the “Company”) and U.S. Bank National Association (the “Trustee”), entered into a Third Supplemental Indenture (the “Third Supplemental Indenture”) to the Indenture, dated July 14, 2014, between the Company and the Trustee (the “Base Indenture”; and together with the Third Supplemental Indenture, the “Indenture”). The Third Supplemental Indenture relates to the Company’s issuance of $275,000,000 aggregate principal amount of its 4.750% notes due 2022 (the “Notes”).

The Notes will mature on May 15, 2022 and may be redeemed in whole or in part at the Company’s option at any time or from time to time at the redemption prices set forth in the Indenture. The Notes bear interest at a rate of 4.750% per year payable semi-annually on May 15^th and November 15^th of each year, commencing on November 15, 2015. The Notes are general unsecured obligations of the Company that rank senior in right of payment to all of the Company’s existing and future indebtedness that is expressly subordinated in right of payment to the Notes, rank pari passu with all existing and future unsecured unsubordinated indebtedness issued by the Company, rank effectively junior to any of the Company’s secured indebtedness (including unsecured indebtedness that the Company later secures) to the extent of the value of the assets securing such indebtedness, and rank structurally junior to all existing and future indebtedness (including trade payables) incurred by the Company’s subsidiaries, financing vehicles or similar facilities.

The Indenture contains certain covenants, including covenants requiring the Company to comply with the asset coverage requirements of Section 18(a)(1)(A) as modified by Section 61(a)(1) of the Investment Company Act of 1940, as amended, whether or not it is subject to those requirements, and to provide financial information to the holders of the Notes and the Trustee if the Company is no longer subject to the reporting requirements under the Securities Exchange Act of 1934, as amended. These covenants are subject to important limitations and exceptions that are described in the Indenture.

In addition, on the occurrence of a “change of control repurchase event,” as defined in the Indenture, the Company will generally be required to make an offer to purchase the outstanding Notes at a price equal to 100% of the principal amount of such Notes plus accrued and unpaid interest to the repurchase date.

The Notes were offered and sold in an offering registered under the Securities Act of 1933, as amended, pursuant to the Registration Statement on Form N-2 (File No. 333-195863), the prospectus supplement dated April 27, 2015 and the pricing term sheet filed with the U.S. Securities and Exchange Commission on April 27, 2015. The transaction closed on April 30, 2015. The net proceeds to the Company were approximately $271.3 million, after deducting the underwriting discounts and commissions of approximately $2.5 million payable by the Company and estimated offering expenses of approximately $350,000 payable by the Company. The Company intends to use the net proceeds to repay outstanding indebtedness under its financing arrangements.

The foregoing descriptions of the Third Supplemental Indenture and the Notes do not purport to be complete and are qualified in their entirety by reference to the full text of the Third Supplemental Indenture and the Notes, respectively, each filed as exhibits hereto and incorporated by reference herein.

The information required by Item 2.03 contained in Item 1.01 of this Current Report on Form 8-K is incorporated herein by reference.

(d) Exhibits.

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