Freshman forward Tobias Harris added 16 points and seven rebounds in 29 minutes for the Volunteers (2-0), who face Missouri State Wednesday for a berth in the tournament semifinals in New York.
Cameron Tatum was the only other Tennessee player to score in double figures. The Vols shot 53.2 percent from the field but made only 3-of-11 from 3-point range.
Belmont (0-1) also had three players in double figures. Ian Clark led the Bruins with 18 points. Drew Hanlen scored 13 points and Mick Hedgepeth added 10.
Tennessee took a 41-35 lead at halftime and outscored Belmont 44-41 in the second half.