Nelson-Henry finished with 18 points, 11 rebounds and three steals for the Quakers (8-20, 5-6 Ivy League), who snapped a two-game losing streak. Henry Brooks and Miles Cartwright each scored 12 points.
Penn, which led by 16 points late in the first half, had its lead trimmed to 69-65 with 1:38 left to play when Harvard's Laurent Rivard knocked down a 3-pointer. The Crimson cut the deficit to three points on Siyani Chambers' 3-pointer with 13 seconds remaining, but two-seconds later, Miles Cartwright answered with two free throws to push the Quakers' lead to five.
Christian Webster's 3-pointer cut the score to 74-72, but that was the last shot Harvard (17-9, 9-3) would attempt.
Wesley Saunders scored 20 points and Webster had 16 points for the Crimson.