By Tim Glon
The Polar Bears improve to 8-8 overall and are 3-6 in the Ohio Athletic Conference, while the Student Princes fall to 7-9, 3-6.
DiOrio had career-highs of 24 points and six rebounds on a perfect 8-for-8 shooting from the floor, including a perfect 6-for-6 from beyond the 3-point arc.
Ellerhorst scored a career-high 11 points as ONU played without two players due to illness.
"We had a couple of guys out sick, so we needed other guys to step up," ONU head coach Kevin Byrne said. "We did a nice job in the second half on both ends of the floor. We shot the ball well and did a good job rebounding the ball."
Trailing 44-35 in the second half, the Polar Bears went on a 10-0 run, capped by a layup from DiOrio, to go up 45-44 with 13:05 left to play.
A 3-pointer by DiOrio put Ohio Northern ahead for good at 50-48 with 10:49 left in the game.
Back-to-back threes by DiOrio extended Northern's lead to 66-55 with 5:21 to play.
HU would get no closer than nine points the rest of the way.
ONU made 27-of-56 field goal attempts for 48.2 percent and was 13-of-27 from 3-point land for 48.1 percent.
Heidelberg made 26-of-64 field goals for 40.6 percent and was 7-of-23 from beyond the 3-point arc for 30.4 percent.
ONU out-rebounded HU 38-31 behind seven boards from senior Lucas Pennington.
The Polar Bears will return to action Saturday at Capital.