The victory keeps Saint Mary's (18-5, 10-2) in second place in the West Coast Conference behind No. 2 Gonzaga.
The Gaels raced to a 10-point lead five minutes into the game. Simmons sandwiched a pair of 3-pointers around an Emmett Naar trey and his own layup to make it 18-8 with 14:41 left in the first half. Pacific scratched its way back, cutting the deficit to five, 24-19 on Ray Bowles' layup with 5:24 remaining in the half, but Saint Mary's closed hard, taking a 39-27 lead at the break.
Kerry Carter contributed 16 points for Saint Mary's and Naar added 13.