The game was knotted at 31 at halftime and 64 at the end of regulation.
Miller made a shot in the lane to give Cornell a 64-62 lead with 1:30 left. Dartmouth's Malik Gill had a steal and missed his layup, but Gabas Maldunas' putback tied it at 64. Miller missed a 17-footer at the buzzer.
Cornell started fast in overtime, but Gill made a 3-pointer to keep Dartmouth within 74-69. After a Miller dunk, Miles Wright hit a 3-pointer to make it 76-72 but Dartmouth would not score again.
Wright led Dartmouth (8-13, 1-6) with 19 points. Gabas Maldunas had 14 points and 12 rebounds as the Big Green had their losing streak extended to five games.