With the score tied at 72, Thompson drove the lane and missed a shot but was fouled with six seconds to play. He made the front end of a one-and-one and missed the second.
The game was part of ESPN's Bracket Buster weekend.
Cal State Northridge managed to hold Rider big man Jason Thompson to just 11 points. Thompson, who averages 20.3 points, had attracted scouts from 12 NBA teams.
Rider (19-9) led virtually the entire game but couldn't shake a pesky Northridge squad despite the Matadors missing its top three post players for most of the second half.
Northridge's Jayme Miller fouled out with 12:57 left and Tremaine Townsend missed 11 minutes of the second half with foul trouble before he fouled out in the closing seconds. Forward Calvin Chitwood was out with an ankle injury.
Josh Jenkins led Northridge (18-7) with 21 points and Tresvant added 18.