Tarik Phillip hit a 3-pointer with 28 seconds left while the shot clock was winding down, adding the clinching points as fifth-seeded
The Mountaineers (24-9) advance to Sunday's game against the winner of 13th-seeded Valparaiso (28-5) and No. 4 Maryland (27-6).
Devin Williams, who led the Mountaineers with 17 points and nine rebounds, hit two free throws with 2:10 left to give his team the lead for good.
Juwan Staten had 15 points and seven assists for West Virginia, with Daxter Miles Jr. adding 10 points.