Stan Okoye finished with 18 points on 5 of 9 shooting, Ron Burks scored 14, Quinton Upshur added 10 for the Keydets, who shot 49 percent (24 of 49) from the floor.
VMI (12-11, 7-6 Big South Conference) led throughout the entire first half and took a 47-36 lead into halftime. But Winthrop opened the second half with a 26-8 run and took a 62-55 lead with 10:56 left to play.
The Keydets rallied back, taking a 79-74 lead with 2:40 left following back-to-back 3-pointers from Okoye and Gabriel.
Gabriel scored six points in the final minute to seal the victory.
George Valentine had 16 points and 11 boards for Winthrop (10-15, 7-7) who won the rebounding battle—38-21.