The victory was the first for the Grizzlies over the Bruins in the five-game history between the two teams.
UCLA (3-4) was hopeful that returning home would help stop a losing streak, but instead lost its fourth in a row. The Bruins were coming off a confidence-building, one-point loss at No. 4 Kansas but weren't able to find their groove against the Grizzlies.
Montana (4-3) held the Bruins to 28 points in the first half by cutting off the inside pass and using a collapsing defense when UCLA was able to get the ball into the paint.
adidas Men's UCLA Bruins Gold Long Sleeve Shooter ShirtPrice: $47.97 Shop
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.