Buffalo led by as many as seven points in the second half, but Kent State fought back and took its first lead in nearly 20 minutes of action when Darren Goodson's free throw put the Golden Flashes ahead, 50-49, with less than 10 minutes remaining.
The Bulls briefly regained a one-point advantage with 3:31 left in the game, but Kent State made its final six free throws and last two field goal attempts to salt away the game.
The Golden Flashes will take on the top-seeded Akron Zips in the semifinal round on Friday.
In the nightcap, the Western Michigan Broncos pulled away from the Eastern Michigan Eagles in the second half on their way to a 70-55 victory. Shayne Whittington led the Broncos with 23 points and 8 rebounds.
The Broncos face the Ohio Bobcats, the MAC's No. 2 seed, after the completion of the Kent State-Akron contest.
An updated MAC Tournament bracket can be found here.