FIU was scheduled to visit Bloomington, Indiana, on Saturday, but the game was canceled as the Miami school continues to deal with impact of Hurricane Irma.
The contract with Charleston Southern was finalized Tuesday, according to an IU news release. Both teams previously had open dates scheduled for Oct. 7. The late addition ensures a sixth home game this season for the Hoosiers and a 12-game regular-season schedule.
Indiana (1-1) beat Virginia in Week 2 after a loss to Ohio State in its opener.
Charleston Southern's Week 2 game against South Carolina State was wiped out by the threat of Irma. CSU lost in the first round of the FCS playoffs to Wofford last season.