Fifth-seeded Virginia rallied from 15 points down to beat 12th-seeded UNC Wilmington 76-71.
London Perrantes scored 24 points, Marial Shayok added a career-high 23 off the bench for Virginia.
Perrantes scored 19 points in the second half as the Cavaliers (23-10) got their slow-paced offense going. His biggest bucket was a driving bank shot with 1:37 remaining, which put the Cavs up 71-66.
UNCW (29-6) wouldn't go away, though. Chris Flemmings drained a 3-pointer from the elbow and then Devontae Cacok hit a layup to make it 73-71 with less than a minute to play. But Shayok answered on the other end, banking in a runner that gave the Cavs some breathing room in the closing seconds.
Virginia advanced past the first round for the fourth consecutive year and won as a No. 5 seed for the first time in four tries. The Cavs can thank Perrantes and Shayok for making it happen.
Perrantes was 9-of-14 shooting, and Shayok was 8 of 14. The guard duo set the pace late after Virginia trailed big.
The Cavaliers closed the first half with a 16-1 run that erased the double-digit deficit.
UNCW was nearly perfect early, with Ambrose Mosley, Denzel Ingram and Cacok hitting every shot they took.
Mosley and Ingram combined for six 3-pointers in the first 12 minutes. Cacok, who leads the nation in field-goal percentage (79.9), made all four of his shots.
The result was a 15-point lead for the Seahawks. They controlled tempo, were seemingly first to every loose ball and looked like they would become the latest No. 12 seed to win in the opening round of the NCAA Tournament.
In the previous five years, half of the 12 seeds (10 of 20) have bounced No. 5 seeds.
And it looked like another early exit for Virginia, which failed to reach the Final Four as a No. 1 or No. 2 in each of the last three years. The Cavaliers also entered the tournament winless as a fifth seed, losing to DePaul (1986), Wyoming (1987) and Gonzaga (2001).
But Perrantes and Shayok didn't let it happen again.