With the victory, the Polar Bears move to 16-4 on the season and 11-3 in the OAC, while Mount Union falls to 5-16 overall and 4-10 in conference play.
ONU has now won five straight games and eight of its last nine.
Junior Bart Hostetler led the Bears with 16 points and five rebounds. Sophomore Kyle Gehle added 14 points and was 4-of-4 from the free throw line for ONU.
Junior Greg Badenhop scored 12 points in the contest, while freshman Jake Cannan chipped in 10 points and five rebounds.
ONU grabbed its largest lead in the second half, 56-46, on Hostetler’s jumper with 8:37 left in the game. However, the Purple Raiders answered with a 10-0 run to tie the game at 56-56 all with 5:51 left.
Mount Union was able to take the lead 57-56 off a pair of LJ Helton free throws, but Ohio Northern re-gained the lead and pushed the score to 71-64 on a pair of free throws by freshman Kurtis Brown with 31 seconds left.
The Purple Raiders answered with a Luke Conley three-pointer with three seconds left to cut the Polar Bears’ advantage to 74-72, but Hostetler made both of his free throws with one second left to give the Bears a four-point lead and the win.
Mount Union gained their largest lead in the first-half, 16-11, off a Helton three-pointer with 10:23 left, but Gehle scored four points for the Bears and a three-pointer by senior Nate Lieb gave ONU an 18-17 lead with 7:56 left until intermission.
A foul shot by Helton gave Mount Union the lead, 30-29, with 1:22 left, but Cannan scored a layup to give the Bears a one-point lead with 1:06 left.
Lieb connected on a three-pointer with 14 seconds left in the first half and the Bears were able to go into the locker room with a 34-30 lead.
The Polar Bears connected on 26-of-48 field goals for 54.2 percent, while the Purple Radiers hit 58.3 percent off of 28-of-48 shots.
ONU grabbed 26 boards, while Mount Union pulled down 21 rebounds.
Mount Union was led by Kyle Karpinski with 17 points, while Helton added 14 point for the Purple Radiers.
Ohio Northern returns to action on Wednesday, Feb. 8, when it travels to Wilmington for a 7:30 p.m. tip-off.