Derrick Gordon scored the game-winning layup off a George Mason turnover with 8.1 seconds left, enabling 16th-ranked Massachusetts to escape with an 88-87 win at the Patriot Center.
The Minutemen trailed 86-81 with 41 seconds remaining before outscoring the Patriots 7-1 the rest of the way.
Chaz Williams finished with 26 points on 11-of-17 shooting and added eight assists in igniting the Minutemen's comeback. Cady Lalanne chipped in 19 points and nine rebounds, while Raphiael Putney had 12 points to help Massachusetts (15-1, 3-0 A-10) prevail.
George Mason (7-10, 0-3) received 26 points from Sherrod Wright and 21 from Bryon Allen in defeat, with Jalen Jenkins recording 16 points and nine rebounds.