Josh Odem added 13 and Chris Early had 10 points and 11 rebounds as the Mocs (15-17) moved into a quarterfinal matchup against College of Charleston on Saturday.
Chattanooga led by as many as 28, pulling away early in the second half after leading 40-29 at halftime. The Mocs dominated inside, gaining a 49-20 rebound advantage with 54 of its 82 points in the paint, and hit 18 of 21 from the field in the second half. Chattanooga shot 66.7 percent from the field for the game.
Chattanooga had lost seven of its previous eight games.
Rory Spencer led Georgia Southern (9-23) with 15 points, and Antonio Hanson and Willie Powers scored 12 each. The Eagles shot 34.4 percent from the field.