Columbia (16-12, 7-7 Ivy League) last won 16 games in 1993. The Lions haven't won 17 games since 1979.
Nwachukwu scored 12 points in the first half. The Lions led by as many as 13 points and 37-26 at intermission.
Harvard (12-16, 5-9) pulled to within 48-43 with 13:35 to play but Patrick Foley hit two free throws and Nwachukwu scored on a putback to give Columbia a nine-point edge with 13:05 remaining.