Jordair Jett added 15 points for the Billikens (12-3), who have won nine straight—their longest streak since winning 14 in a row to start the 1993-94 season.
Cady Lalanne had 18 points and 13 rebounds for Massachusetts (10-4), which had its seven-game winning streak snapped. Chaz Williams added 14 points and seven assists.
Massachusetts used a 3-pointer from Freddie Riley, a tip-in by Lalanne and another 3 by Williams to take a 54-50 lead with 9:28 remaining. Back-to-back layups by Jett capped a 7-0 run that put Saint Louis back in front for good, and UMass made only 2 of 11 shots the rest of the way.