The Pacers led by 14 with just over nine minutes remaining in the second half, but couldn’t hold on.
Columbus State’s Winford Ivey hit a pair of free throws with 7 seconds left to to send the game into overtime tied at 77.
The Cougars outscored the Pacers 18-13 in the extra session.
Ronald Zimmerman led USC Aiken (7-4, 3-1 Peach Belt) with 27 points, including six 3-pointers.
Rory Miller had 25 points and 11 boards for Columbus State (6-1, 1-3).