The Stags (6-11, 4-3 Mid-Atlantic Athletic Conference) were leading 46-45 when Marcus Gilbert made a free throw with 5:02 to play. Marist then missed three 3-pointers, an inside attempt and had a turnover on its next three possessions while K.J. Rose and Tyler Nelson scored to put Fairfield up 51-45 at 3:19.
Chavaughn Lewis, who led the Red Foxes (1-16, 0-6) with 22 points, ended a near four-minute drought with a layup but Marist remained cold while Steve Johnson and Nelson combined to go 8-8 from the foul line in the final minute to secure the win.
Fairfield finished 27 of 36 from the line while Marist was 12 of 15 in losing its 12th straight.
T.J. Curry added 11 points for Marist.