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 26, 2014

FS Investment Corporation III

(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:

Item 1.01.        Entry into a Material Definitive Agreement.

On June 26, 2014, Center City Funding LLC (“Center City Funding”), a newly-formed, wholly-owned financing subsidiary of FS Investment Corporation III (the “Company”), entered into a total return swap (“TRS”) for a portfolio of senior secured floating rate loans with Citibank, N.A. (“Citibank”).

A TRS is a contract in which one party agrees to make periodic payments to another party based on the change in the market value of the assets underlying the TRS, which may include a specified security, basket of securities or securities indices during a specified period, in return for periodic payments based on a fixed or variable interest rate. A TRS effectively adds leverage to a portfolio by providing investment exposure to a security or market without owning or taking physical custody of such security or investing directly in such market. Because of the unique structure of a TRS, a TRS often offers lower financing costs than are offered through more traditional borrowing arrangements.

The TRS with Citibank enables the Company, through its ownership of Center City Funding, to obtain the economic benefit of owning the loans subject to the TRS, without actually owning them, in return for an interest-type payment to Citibank. As such, the TRS is analogous to Center City Funding borrowing funds to acquire loans and incurring interest expense to a lender.

The obligations of Center City Funding under the TRS are non-recourse to the Company and the Company’s exposure under the TRS is limited to the value of the Company’s investment in Center City Funding, which generally will equal the value of cash collateral provided by Center City Funding under the TRS. Pursuant to the terms of the TRS, Center City Funding may select a portfolio of loans with a maximum aggregate market value (determined at the time each such loan becomes subject to the TRS) of $100.0 million. Center City Funding is required to initially cash collateralize a specified percentage of each loan (generally 25% of the market value of such loan) included under the TRS in accordance with margin requirements described in the agreements between Center City Funding and Citibank that collectively establish the TRS (collectively, the “TRS Agreement”). Under the terms of the TRS, Center City Funding has agreed not to draw upon, or post as collateral, such cash collateral in respect of other financings or operating requirements prior to the termination of the TRS. Neither the cash collateral required to be posted with Citibank nor any other assets of Center City Funding are available to pay the debts of the Company.

Pursuant to the terms of an investment management agreement (the “Investment Management Agreement”) that the Company has entered into with Center City Funding, the Company acts as the investment manager of the rights and obligations of Center City Funding under the TRS, including selecting the specific loans to be included in the portfolio of loans subject to the TRS. Accordingly, the loans selected by Center City Funding for purposes of the TRS are selected by the Company in accordance with its investment objectives and strategy to generate current income and, to a lesser extent, long-term capital appreciation. In addition, pursuant to the terms of the TRS, Center City Funding may select any loan or obligation available in the market to be included in the portfolio of loans that meets the obligation criteria set forth in the TRS Agreement.

Each individual loan, and the portfolio of loans taken as a whole, must meet criteria described in the TRS Agreement, including a requirement that substantially all of the loans underlying the TRS be rated by Moody’s Investors Services, Inc. and Standard & Poor’s Rating Services and quoted by a nationally-recognized pricing service. Under the terms of the TRS, Citibank, as calculation agent, determines whether there has been a failure to satisfy the portfolio criteria in the TRS. If such failure continues for 30 days following the delivery of notice thereof, then Citibank has the right, but not the obligation, to terminate the TRS. Center City Funding receives from Citibank all interest and fees payable in respect of the loans included in the portfolio. Center City Funding pays to Citibank interest at a rate equal to the one-month London Interbank Offered Rate, or LIBOR, plus 1.30% per annum on the full notional amount of the loans subject to the TRS. In addition, upon the termination or repayment of any loan subject to the TRS, Center City Funding will either receive from Citibank the appreciation in the value of such loan or pay to Citibank any depreciation in the value of such loan.

Under the terms of the TRS, Center City Funding may be required to post additional cash collateral, on a dollar-for-dollar basis, in the event of depreciation in the value of the underlying loans after such value decreases below a specified amount. The limit on the additional collateral that Center City Funding may be required to post pursuant to the TRS is equal to the difference between the full notional amount of the loans underlying the TRS and the amount of cash collateral already posted by Center City Funding. The amount of collateral required to be posted by Center City Funding is determined primarily on the basis of the aggregate value of the underlying loans.

The Company has no contractual obligation to post any such additional collateral or to make any interest payments to Citibank. The Company may, but is not obligated to, increase its equity investment in Center City Funding for the purpose of funding any additional collateral or payment obligations for which Center City Funding may become obligated during the term of the TRS. If the Company does not make any such additional investment in Center City Funding and Center City Funding fails to meet its obligations under the TRS, then Citibank will have the right to terminate the TRS and seize the cash collateral posted by Center City Funding under the TRS. In the event of an early termination of the TRS, Center City Funding would be required to pay an early termination fee.

Citibank may terminate the TRS on or after June 26, 2015, the first anniversary of the effectiveness of the TRS. Center City Funding may terminate the TRS at any time upon providing no more than 30 days, and no less than 10 days, prior notice to Citibank. Any termination prior to the first anniversary of the effectiveness of the TRS will result in payment of an early termination fee to Citibank based on the maximum notional amount of the TRS. Under the terms of the TRS, the early termination fee will equal the present value of a stream of monthly payments which would be owed by Center City Funding to Citibank for the period from the termination date through and including June 26, 2015. Such monthly payments will equal the product of (x) 80%, multiplied by (y) the maximum notional amount of the TRS ($100.0 million), multiplied by (z) 1.30% per annum. Other than during the first 90 days and last 30 days of the term of the TRS, Center City Funding is required to pay a minimum usage fee if less than 80% of the maximum notional amount of the TRS is utilized and an unused fee on any amounts unutilized if greater than 80% but less than 100% of the maximum notional amount of the TRS is utilized.

In connection with the TRS, Center City Funding has made customary representations and warranties and is required to comply with various covenants, reporting requirements and other customary requirements for similar facilities. Included among the customary events of default and termination events in the TRS Agreement are: (a) a failure to satisfy the portfolio criteria or obligation criteria for at least 30 days; (b) a failure to post initial cash collateral or additional collateral as required by the TRS Agreement; (c) a default by Center City Funding or the Company with respect to indebtedness in an amount equal to or greater than the lesser of $10.0 million and 2% of the Company’s net asset value at such time; (d) Center City Funding ceasing to be our wholly-owned subsidiary; (e) either the Company or Center City Funding amending its constituent documents to alter its investment strategy in a manner that has or could reasonably be expected to have a material adverse effect; (f) the Company ceasing to be the investment manager of Center City Funding or having authority to enter into transactions under the TRS on behalf of Center City Funding, and not being replaced by an entity reasonably acceptable to Citibank; (g) FSIC III Advisor, LLC (or an entity reasonably acceptable to Citibank) ceasing to be the Company’s investment adviser or GSO / Blackstone Debt Funds Management LLC (or an affiliate) ceasing to be the investment sub-adviser to FSIC III Advisor, LLC; (h) Center City Funding failing to comply with its investment strategies or restrictions to the extent such non-compliance has or could reasonably be expected to have a material adverse effect; (i) Center City Funding becoming liable in respect of any obligation for borrowed money, other than arising under the TRS Agreement; (j) the Company dissolves or liquidates; (k) there occurs, without the prior consent of Citibank, any material change to or departure from the Company’s policies or the policies of Center City Funding that may not be changed without the vote of the Company’s stockholders and that relates to Center City Funding’s performance of its obligations under the TRS Agreement; and (l) the Company violates certain provisions of the Investment Company Act of 1940, as amended (the “1940 Act”), or the Company’s election to be regulated as a business development company (“BDC”) under the 1940 Act is revoked or withdrawn.

For purposes of the asset coverage ratio test applicable to the Company as a BDC, the Company will treat the outstanding notional amount of the TRS, less the initial amount of any cash collateral required to be posted by Center City Funding under the TRS, as a senior security for the life of that instrument. The Company may, however, accord different treatment to the TRS in the future in accordance with any applicable new rules or interpretations adopted by the staff of the Securities and Exchange Commission (the “SEC”).

Further, for purposes of Section 55(a) under the 1940 Act, the Company will treat each loan underlying the TRS as a qualifying asset if the obligor on such loan is an eligible portfolio company and as a non-qualifying asset if the obligor is not an eligible portfolio company. The Company may, however, accord different treatment to the TRS in the future in accordance with any applicable new rules or interpretations adopted by the staff of the SEC.

The summary descriptions of the TRS Agreement and the Investment Management Agreement are summaries only and are qualified in all respects by the provisions of such agreements, copies of which are attached hereto as Exhibits 10.1, 10.2 and 10.3 and are incorporated herein by reference.

Item 9.01.        Financial Statements and Exhibits.

(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