Montana's Ahmaad Rorie tied the game at 77 with 30 seconds left. The Vandals ran down the clock before Blake drove the lane and his running jumper rimmed out, but Sherwood tapped in the ball to end the only regular season meeting between the teams.
Idaho (19-7, 11-3 Big Sky Conference), which beat the Grizzlies in last season's tournament quarterfinals, remains in third place in the conference standings behind Montana and Weber State (12-2). The Vandals travel to Weber State next Saturday.
Montana (20-7, 13-2) has lost two straight since having its 13-game winning streak snapped in a nine-point loss to Eastern Washington on Thursday.
Victor Sanders added 21 points for the Vandals. Sherwood finished with eight points and seven rebounds.
Rorie scored 21 points to lead four in double-figure scoring for Montana. Fabijan Krslovic made the first of two free-throw attempts for Montana to tie it at 71 with 46 seconds remaining in regulation. Jamar Akoh blocked Sherwood's jumper with 22 seconds left, but Rorie and Bobby Moorehead missed shots to force overtime.
CSU Bakersfield tops Cal Poly for 4th straight win
Justin Edler-Davis sank 9 of 10 free throws and scored 15 points and Cal State Bakersfield ran its winning streak to four with a 74-61 victory over Cal Poly on Tuesday night.
No. 11 Florida State looks for fifth straight win vs. North Florida
The Florida State men's basketball team's eight-game home winning streak was tested Monday by Southeast Missouri State, but the No. 11 Seminoles found a way to turn an 11-point first-half deficit into a 17-point win, 85-68, to move to 9-1.
Burnell leads Jacksonville State past North Alabama, 64-50
Jason Burnell had 19 points and nine rebounds and Marlon Hunter scored 15 to help Jacksonville State beat North Alabama 64-50 on Tuesday night.