Fairfield (10-9, 4-5 Metro Atlantic) pulled away late with a 9-2 run capped by Marcus Gilbert's 3-pointer that made it 81-72 with 2:09 left.
Matija Milin added 12 points, Jonathan Kasibabu scored 10 and Jerome Segura had 11 assists with six points. The Stags shot 62 percent (31 of 50) and made 7 of 8 free throws in the final 1:22 to secure the win.
Marist (4-13, 1-7) stretched a one-point halftime lead to 47-41 to start the second. The Stags regained the lead for good at 55-54 on Kasibabu's basket during an 11-1 run.