Clitan De Sousa hit the go-ahead bucket with 20 seconds to go and No. 25 West Virginia did not have a rebuttal as the Mountaineers (13-4, 3-3 in Big 12) fell to Oklahoma State (12-6, 3-3 in Big 12), 57-55.
The Mountaineers were led in scoring by 11 points from Kysre Gondrezick while Kari Niblack added 9 points and 10 rebounds.
The Cowgirls' Vivian Gray led all scorers with 22 points.
West Virginia has lost three straight games for the first time in nearly two years. The team will travel to Fort Worth, Texas to take on TCU this Sunday on FS1.