The top-seeded Mustangs (24-9) overcame a 30-29 halftime deficit and a sub-par shooting night (33.9% from the field) to handle the Anteaters (23-12), who posted the second-most victories in program history.
Big West Conference Freshman of the Year Luke Nelson had a team-best 13 points and added five rebounds and four assists, while junior Will Davis had nine points, 11 rebounds and one blocked shot.
Mamadou Ndiaye, UCI's 7-foot-6 freshman center, had seven points, 12 rebounds (tying his career best) and seven blocked shots to up his Big West single-season block record total to 106.
Sophomore Alex Young had 10 points and five assists for UCI, for which Chris McNealy, the team's lone senior, had nine points and four rebounds.
UCI, the Big West regular-season champion was 19 of 52 from the field (36.5%) and was just six for 20 from three-point range (30%). It shot just 24.1% from the feild in the second half (seven for 29).
The 'Eaters won the rebounding battle, 43-39, but had 20 turnovers, 12 more than the hosts, and made just 10 of 14 from the foul line. SMU made 23 of 34 free-throw attempts, to overcome its 33.9% field-goal shooting (20 for 59).
It was the first time in 22 games this season that UCI lost when holding its opponent to worse than 40% shooting from the field.
UCI opened with a 7-0 lead and held SMU scoreless for 4:24. Coach Russell Turner's visitors led, 27-20, and 30-22, but the hosts, coached by Hall of Famer Larry Brown, scored the final seven points of the half.
SMU took its first second-half lead at 37-35 with 15:29 left and a Nelson jumper pulled UCI back within 41-39 with 12:45 remaining.
SMU extended the lead, but two Ndiaye free throws pulled the visitors within 58-52 with 3:07 left, before the Mustangs, ranked No. 18 on March 3, pulled away to advance to the second round.
"[The Mustangs] came after us and created a lot of offense with their defense," Turner told reporters afterward. "It was a great atmosphere for a college basketball game and I give SMU credit."
Cannen Cunningham, who was nine for 12 from the foul line, had 17 points and seven rebounds to lead the winners.
— From staff reports