North Dakota (11-13, 8-6) made just 3 of 6 free throws in the final minute but it was enough to hold off the Grizzlies (12-11, 7-7).
North Dakota was up 71-57 with 4:11 to play when the Grizzlies reeled off eight-straight points to pull within six with 1:57 to go but ultimately Montana could not overcome 17 turnovers.
The Grizzlies shot 54.5 percent and went 16 of 19 from the foul line. They had a 30-27 rebounding advantage but UND had 11 offensive boards, which provided 13 more shots than UM got.
Nash had 17 at the half as North Dakota led 38-33.