Cameron Johnson scored 21 points, and North Carolina quickly erased a five-point halftime deficit to hot-shooting Iona, going on to win 88-73 on Friday night.
The Tar Heels (28-6), who came into the tournament as a top seed for a record 17th time, advanced to play Washington in the second round of the Midwest Region on Sunday. They're hoping to reach their 11th Final Four.
Much like Gardner-Webb did earlier Friday against No. 1 seed Virginia - which last year became the first top seed to lose in the first round - Iona surprised the Tar Heels early with their energy and outside shooting. Ricky McGill made all four of his 3-point attempts in the opening half as the Gaels (17-16) led by as many as eight and took a 38-33 lead into halftime.
Iona's advantage disappeared quickly. Johnson's 3-pointer and Luke Maye's jumper tied it 39 seconds into the second half, and an 18-4 run put North Carolina back on track.
The bigger and stronger Tar Heels dominated the boards, outrebounding Iona 52-26 and getting 25 second-chance points. After shooting 44.3 percent the first half, they hit 63 percent in the second and led by as many as 20 points.
McGill finished with 26 points, including 7-for-9 shooting from beyond the arc for the Metro Atlantic Athletic Conference champion Gaels, who are one-and-done in the tournament for the fourth straight season. They're still seeking their first NCAA win after 13 trips.
Asante Gist had 17 points and Andrija Ristanovic scored 11 for Iona.
Nassir Little added 19 points for UNC.
Iona: The Gaels hit 10 of 21 3-point tries in the first half but managed just five more on 20 tries the rest of the way. They couldn't overcome the missed shots as they were beaten up on the boards.
North Carolina: The Tar Heels won't have the luxury of playing as poorly as they did in the first half if they want to make a deep tournament run.
North Carolina plays Washington in next round.
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