The Purple Eagles (1-1 Metro Atlantic Athletic Conference) shot 45.7 percent from the floor (21 of 46) to 42 percent (21 of 50) for St. Peter's.
Dominique Marvin led the Peacocks with 18 points and 13 rebounds, his 14th career double-double. Chazz Patterson scored 12 points.
The lead changed hands five times in the first half before St. Peter's pulled ahead 17-11 on a 9-2 run, but Niagara tied it at 19 on back-to-back 3-pointers by Snowden and led 24-20 at halftime.
Niagara led 49-39 at 8:28 on a jumper by Emile Blackman, but St. Peter's (0-3) came back, pulling to within two points 58-56 on a 3-pointer by Gaskins Tyler at 2:04. Karonn Davis replied with a trey for Niagara and the Peacocks' Patterson missed a jumper with 9 seconds left.