The Stags (6-22, 3-14 Metro Atlantic Athletic Conference) shot 41.4 percent from the field and hit 11 of 19 3-pointers. Steve Johnston scored 14 points and Amadou Sidibe had nine with 10 rebounds. K.J. Rose dished out nine of Fairfield's 20 assists.
Niagara (6-22, 3-14) shot 41.9 percent, but went 3 of 12 beyond the arc and 11 of 25 from the foul line. Antoine Mason scored 22 points and Wesley Myers had 17.
Fairfield closed the first half on a 15-4 run fueled by Gilbert with two layups, a 3-pointer and a jumper to grab a 34-24 halftime advantage.
The Purple Eagles narrowed the gap to four in the second half, but two Johnston 3-pointers with a Gilbert trey in between made it 67-56 with 2:09 left.