Joston Thomas rolled a shot around the rim and 82, comeback victory over No. 14 Xavier in the consolation bracket of the Diamond Head Classic.
Thomas recorded a career-high 24 points to go along with nine rebounds in Hawaii's (6-5) first win over a ranked team since beating fourth-ranked Michigan State on November 19, 2005.
Vander Joaquim added 20 points and seven rebounds, Zane Johnson dropped in 14 points and Hauns Brereton had 13, including the game-tying three-pointer with two seconds left in the second half for the Rainbow Warriors.
Xavier (8-3) saw its second-highest scorer, Mark Lyons, return from a two-game suspension after a bench-clearing brawl against Cincinnati on December 10, but that could not stop the Musketeers from dropping their third straight game for the first time under third-year head coach Chris Mack.
Lyons had 18 points, while Tu Holloway, who returned from a one-game ban on Thursday against Long Beach State, had a season-high 26 points.
Trailing by a score of 61-46 with 13:52 to go in the second half, a pair of free throws by Joaquim sparked an 18-5 run by the Rainbow Warriors to bring them within two.
Joaquim had eight points in the swing, which lasted almost eight minutes and was capped by two Thomas free throws to make it a 66-64 contest.
Lyons made a layup and then a couple from the charity stripe to stretch Xavier's lead to six, but Johnson answered with a trey and a layup to make it a one-point game with 4:50 to go in regulation.
The teams traded buckets over the next four possessions, including back-to- back three-pointers by Holloway and Johnson, but then neither team made a shot until Holloway's pull-up jumper bounced off the rim twice before falling in for a 77-74 Xavier lead with 24 seconds left.
Johnson had a chance to tie the game on Hawaii's next touch, but his shot rimmed out and Xavier's Kenny Frease grabbed the rebound and was immediately fouled.
However, Frease missed both of his free throws and Brereton grabbed the ball off a screen and sank a three-pointer with 2.0 showing on clock to knot the game at 77 and send it into overtime.
Hawaii's first lead of the contest came on the opening touch of the extra period, which Joaquim finished with a dunk.
After Lyons answered with a bucket, Hawaii scored the next three points to take an 82-79 advantage with 1:54 left in the extra frame.
Then, with Xavier trailing 82-81 in the closing seconds, Holloway had a long two-point jumper bank off the rim as the shot clock wound down, but Xavier's Travis Taylor came down with the offensive rebound before getting fouled, making 1-of-2 free throws to tie the game at 82 with 12 seconds left.
Coming out of a timeout, Johnson took the ball inside and dished it to Thomas on the right side of the basket, where he rolled the ball off his fingers and onto the rim, watching as it did a full rotation before dropping in with 0.2 seconds on the clock for the game-winner.
The Musketeers opened the game with a 12-0 run to take the early lead, making their first five shots while Hawaii missed its first six attempts from the floor.
The Rainbow Warriors would pull within six at 22-16 with a 7-2 spurt near the midpoint of the first half, but Xavier responded by scoring 11 of the next 14 points and took a 45-34 lead into the break.
This was the second meeting between the teams. Xavier won the previous meeting with Hawaii, 70-58, back in 2002...Xavier finished the game shooting 43.5 percent from the floor, while Hawaii shot 47.7 percent...Xavier held a 40-39 advantage on the glass.