Johnny O'Bryant III and Shavon Coleman both poured in 13 points for LSU (20-13), which will play SMU in the second round. Jordan Mickey tallied eight points and eight rebounds for the visitors.
Cole Dickerson scored a game-high 24 points and added eight rebounds as USF's (21-12) season came to a close. Tim Derksen netted 12 off the bench and Kruize Pinkins hauled in 10 rebounds.
Both teams shot an identical 14-of-32 from the field in the first half with two 3-pointers apiece, but LSU made all three of its free-throw tries while USF was scoreless at the stripe, as the Tigers took a 33-30 lead into the halftime locker room.
The Tigers never relinquished the lead after intermission, running their advantage up to as many as 16 with 8:15 to play.
USF shot a dreadful 3-of-23 from 3-point range on the evening, while LSU was 8-of-22 from beyond the arc.