The RedHawks (13-17, 9-7 Mid-American Conference) had lost four of five but shot 50 percent from the field (26 of 52) and blocked nine shots to send Buffalo (17-11, 9-7) to just its second loss in eight games.
Miami opened the second half on a 12-6 run to take a 45-35 lead on Kramer Soderberg's 3-pointer with 14:43 to play. Mavunga scored the first five points of the run.
Antonio Ballard had 13 points and nine rebounds for Miami.
Watt finished with 17 points and Pierce added 16 for Buffalo. Calvin Betts had 12 rebounds for the Bulls.