Jaylen Bland added 10 points, while Steven Thornton and Austin Quick had nine apiece for Riverside (10-11, 3-4 Big West), which shot just 19 of 52 from the field (36.5 percent) but held a 24-8 advantage in made free throws.
Riverside trailed by 11 midway through the first half after Taelin Webb's 3-pointer gave Northridge (6-17, 2-6) a 20-9 lead. Steven Thornton hit a 3 at the other end to ignite a 17-4 run to give the Highlanders their first lead of the game.
In the second half, Riverside took the lead for good with Alexander Larson's jumper with 10:45 left to make it 46-45 and the Highlanders hung on down the stretch.
Landon Drew led Northridge with 16 points.