LaDontae Henton and Kadeem Batts each recorded a double-double for the fourth- seeded Friars (21-11), who advanced to the semifinals of the Big East tourney for the first time in 17 years. Henton had 16 points and 11 rebounds and Batts finished with 13 and 12.
Providence will next face Seton Hall on Friday after the eighth-seeded Pirates stunned third-ranked Villanova on Sterling Gibbs buzzer-beating shot.
D'Angelo Harrison tallied 21 points, 10 boards and four assists for fifth- seeded St. John's (20-12), which nearly climbed out of a 17-point hole.
The Friars appeared to own a comfortable lead after a Henton layup made it 63-46 with 6:24 remaining. The Red Storm, however, used a 22-6 run to get within 69-68 with 1:15 to play.
Harrison then made contact with Bryce Cotton while going for a steal. The foul sent Cotton, who was 1-of-10 from the floor, to the free-throw line and he sank both attempts with 31 seconds remaining. Cotton made four more free throws to wrap up a 10-for-13 effort at the charity stripe.
Rysheed Jordan added 17 points for St. John's.