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: July 26, 2013

(Date of earliest event reported)

Forbes Energy Services Ltd.

(Exact Name of Registrant as Specified in Its Charter)

(361) 664-0549

(Registrant’s Telephone Number, Including Area Code)

N/A

(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 (see General Instruction A.2. below):

Item 1.01 – Entry into a Material Definitive Agreement.

On July 26, 2013, Forbes Energy Services Ltd., or the Company, together with certain of its domestic subsidiaries, Forbes Energy Services LLC, Forbes Energy International, LLC, TX Energy Services, LLC, C.C. Forbes, LLC and Superior Tubing Testers, LLC, or the Borrower Subsidiaries, entered into an amendment dated as of July 25, 2013, or the Third Amendment, to its loan and security agreement, dated as of September 9, 2011, or the Loan Agreement, with Regions Bank, SunTrust Bank and Capital One Leverage Finance Corp., as lenders, and Regions Bank, as agent for the secured parties, or the Agent.

The Third Amendment modifies certain provisions of the Loan Agreement to, among other things, (i) extend the term of the Loan Agreement to July 26, 2018, (ii) increase the maximum borrowing credit to $90 million, (iii) decrease the revolving interest rate whereby borrowings under the Loan Agreement will bear interest at a rate equal to either (a) the LIBOR rate plus an applicable margin of between 2.00% to 2.50% based on borrowing availability or (b) a base rate plus an applicable margin of between 1.00% to 1.50% based on borrowing availability, where the base rate is equal to the greater of the prime rate established by Regions Bank, the overnight federal funds rate plus 0.5% or the LIBOR rate for a one month period plus 1% and (iv) amend various requirements under the Loan Agreement with respect to the Borrower Subsidiaries’ obligation to deliver collateral reports and monthly financial statements. A fee of 0.375% per annum will accrue on the unutilized availability on the newly expanded credit facility. Except as set forth in the amendment, the loan and security agreement, as previously amended, remains in full force and effect.

The foregoing description is a summary and is qualified in its entirety by reference to the Third Amendment, a copy of which is attached hereto as Exhibit 10.1.

Item 2.03 – Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The disclosure required by this item is included in Item 1.01 above and is incorporated herein by reference

Item 9.01 – Financial Statements and Exhibits

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 thereunto duly authorized.