UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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): October 28, 2012

NEUTRAL TANDEM, INC.

(Exact name of registrant as specified in its charter)

550 West Adams Street

9th Floor

Chicago, Illinois 60661

(Address of principal executive offices, including Zip Code)

(312) 384-8000

(Registrant’s telephone number, including area code)

(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 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Separation Agreement with Robert M. Junkroski

As previously announced by Neutral Tandem d/b/a Inteliquent (the “Company”), Robert M. Junkroski stepped down as the Company’s Chief Financial Officer effective October 1, 2012 and will remain employed with the Company until November 1, 2012 to assist with the transition of his responsibilities. Effective October 28, 2012, the Company and Mr. Junkroski entered into a separation agreement and general release (the “Junkroski Separation Agreement”).

Under the terms of the Junkroski Separation Agreement, in lieu of any payments payable to Mr. Junkroski pursuant to his existing employment agreement, Mr. Junkroski will receive an amount equal to twelve months’ base salary, calculated at a rate of $310,000 per annum, which will be paid in equal bi-weekly installments in accordance with the Company’s regular payroll payment schedule; provided that any payments that would otherwise be made during the six months following termination shall instead be paid on May 1, 2013 (which accumulated payment shall include interest at the prime rate plus two percent). Mr. Junkroski will also receive a lump sum payment in the amount of $46,500, payable no later than November 12, 2012. Mr. Junkroski may continue to participate in the Company’s health insurance plan as a retired executive upon payment of the COBRA rate for such health insurance coverage so long as the Company maintains a health insurance plan permitting such participation. The Junkroski Separation Agreement provides for the acceleration of vesting of those stock options and restricted stock awards previously granted to Mr. Junkroski that would have otherwise vested within 18 months of his departure. Mr. Junkroski will also retain his previously vested stock options and restricted stock awards. Mr. Junkroski will have 18 months to exercise his vested options.

Mr. Junkroski agreed to abide by certain non-disparagement provisions and release the Company from any claims arising out of or based upon any events or circumstances occurring on or prior to October 20, 2012.

A copy of the Junkroski Separation Agreement is attached hereto as Exhibit 10.1 and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d) 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 hereunto duly authorized.

EXHIBIT INDEX