McAdoo was starting in place of John Henson, who has missed three straight games for the Tar Heels with a sprained left wrist. Tyler Zeller finished with 17 points and 15 rebounds for Carolina (30-5), which advanced to a third-round game Sunday against eighth-seeded Creighton in the Midwest Region.
Creighton advanced Friday with a 58-57 win over ninth-seeded Alabama.
Kendall Marshall had 11 points and 10 assists and Harrison Barnes scored 14 for the Tar Heels.
Sandro Carissimo scored 11 points and Matt Glass had 10 for the Catamounts (24-12), who got into the tournament by winning the America East Tournament.