The Billikens won their 10th straight game and remained in the lead in the Atlantic 10 Conference.
Saint Louis had only a two-point halftime lead, but dominated the second 20 minutes. The Billikens held the Hawks to 15 field goals and Saint Joseph's went just 3-of-17 from 3-point range.
Rob Loe added 11 points for Saint Louis (22-5, 11-2 A-10), which has a one-game lead in the league race over Virginia Commonwealth.
Ronald Roberts scored 25 points to pace Saint Joseph's (15-11, 6-7).