Herbie Allen added 17 for the Stags (17-14, 10-9 MAAC), who shot 50 percent from the floor. Yorel Hawkins added 12 points and 11 rebounds.
Darryl Crawford scored 21 points for the Jaspers (16-14, 9-10 MAAC), while Chris Smith added 14.
Fairfield led 25-24 at halftime but that edge was erased by a 13-0 Manhattan run. Fairfield countered with a 12-2 run of its own early in the second half, punctuated by Greg Nero's 3-point play, to take the lead for good with 12:33 to go. Nero finished with 11 points.