Sanders was 11-of-17 shooting for the fourth-seeded Stags (19-13), who will play in the tournament championship Monday.
Fairfield shot 59.6 percent from the field (31 of 52), and the Gaels also shot well, making 50.9 percent from the field (26 of 51). But the Stags came down with most of the misses, outrebounding Iona 32-20.
The Stags trailed 60-54 with 10:43 to play before going on a 16-1 run, sparked by nine points from Sanders.
Colin Nickerson and Keith Matthews added 14 points each, and Ryan Olander 11 for the Stags.
Scott Machado led the Gaels (25-7) with 24 points and seven assists. Mike Glover added 19 points for Iona, which led the nation in scoring with 83.5 points per game coming in.