The game was tied at 36 after a first half that featured eight ties and 14 lead changes.
The Bears (7-14, 4-6 Atlantic Sun Conference) never trailed in the second. Ahead 56-55 with 8:02 left, they used a 13-5 run over the next 5 minutes to lead by nine.
The Owls (5-15, 3-7) got within four at 74-70 with 34 seconds left, but Mercer hit 4 of 4 free throws and Kennesaw State missed two field goals.
The Bears, who have won three of their last four games, made 9 of 12 free throws in the final 1:24.
Mercer had a 36-29 rebounding edge, with Mills grabbing nine rebounds and Moore eight.