The Gaels (17-6, 10-2 Metro Atlantic) were without second-leading scorer A.J. English (20.7 ppg), who had to sit out because of his role in a skirmish at the end of last Saturday's overtime win against St. Peter's.
Iona made 30 of 35 free throws, the last by Laury with eight seconds left to secure the win. Laury finished 8 of 11 from the line while Casimir was 12 for 12. Kelvin Amayo went 9-9 and had 17 points.
Marquis Wright led Siena (9-13, 6-7), which was 17-23 from the foul line, with 19 points and Lavon Long had 17 points.
Laury had 17 points as Iona took a 46-42 lead at the half. The Gaels were up 69-56 after two Amayo free throws midway through the second half.
Evan Hymes made two free throws for Siena to make it 86-83 with nine seconds left.