Maddox was the only player to score in double figures for the Tigers (19-4, 7-0), who won their ninth in a row. The senior forward also had six rebounds and five turnovers.
Princeton trailed 55-53 with 2:29 left in the game after Cornell's Chris Wroblewski made two free throws. But Maddox, who shot 8 of 10 from the floor, scored on a layup then knocked down the go-ahead jumper to put Princeton ahead.
The Big Red (6-16, 2-6) had a couple of chances to tie or win the game. Mark Coury attempted a jumper but had his shot blocked by Maddox. Drew Ferry got the rebound then shot a 3-pointer, but it missed.
Wroblewski led Cornell with 14 points, Errick Peck had 13 and Coury added 10.