Thomas grabbed seven rebounds while Aaron Craft added nine points and six boards as the Buckeyes (26-7) used a swarming defense to shut down the Badgers' attack.
Ohio State socked away its third Big Ten tourney title in four years with an 11-2 run down the stretch.
With the victory, the Buckeyes were likely to earn a No. 2 seed in the NCAA Tournament.
Wisconsin (23-11), which will earn an at-large NCAA berth, got 10 points from Traevon Jackson in the loss.