Mason made a 3-pointer that gave Niagara a 60-56 lead and sparked a 14-5 run during which Mason hit two more to put the Purple Eagles up 70-61 with 2:59 left.
Niagara went ahead 47-40 with 14:31 left to play, but Marist took its first lead of the second half at 51-50 on Khallid Hart's layup with 9:47 to go.
The teams exchanged the lead three times and tied twice before Marcus Ware's free throw gave Niagara (6-15, 3-7 Metro Atlantic Athletic Conference) the lead for good at 57-56.
Chavaughn Lewis had 25 points to lead Marist (6-13, 3-6) which shot 28 of 52 from the floor and out-rebounded the Eagles 31-27, but couldn't overcome 16 turnovers.
UMBC coach Ryan Odom nearly doubled his base pay after the program became the first 16th-seeded men's team to win an NCAA tournament game.
Who are the best prospects in the 2018 NBA draft? You can find our updated top 100 rankings here throughout the season.
Andrew Jones, the Texas guard who missed much of his sophomore season while undergoing treatment for leukemia, has been cleared to enroll in online classes this summer and will move back into a dorm room on campus, the university announced Thursday.