Dartmouth's Connor Boehm scored to tie it at 60 with 1:36 remaining. Jaleen Smith hit a jumper and Tanner Leissner made 1 of 2 free throws to give New Hampshire a 63-60 lead with 34 seconds left. Dartmouth answered with Alex Mitola draining a trey with 20 seconds to go before Dion scored the game-winner. Malik Gill's 3-pointer was off the mark as time expired.
Ronnel Jordan scored 15 points and Leissner added 13 for New Hampshire (3-2).
Leissner scored to give the Wildcats a 42-34 lead at the 14:23 mark. Gill's trey capped a 14-4 run to give the Big Green 48-46 lead with 9:25 to go.
Boehm had 14 points, Mitola 13 and Gill 10 to lead Dartmouth (1-3).