The Tigers (16-9, 9-2) had tightened the race for the league’s NCAA tournament berth Friday night with a 58-53 victory over Harvard, whose 75-72 loss to Penn on Saturday night dropped the Crimson to 9-3 in the league.
The Tigers, however, will go on the road for their final three Ivy contests, while Harvard will play its last two at home. If they finish tied, they would meet in a playoff for the second time in three seasons.
Barrett hit two 3-pointers during an 11-2 second-half run that gave the Tigers a 45-33 lead with 9:16 left.
T.J. Bray added 21 points for Princeton.
Tyler Melville had 23 points for Dartmouth (7-19, 3-9), and Gabas Maldunas had 17 points and 12 rebounds.