Niagara's Marvin Jordan's 3-point attempt rimmed the goal at the buzzer, setting off a celebration by Retriever players and fans at midcourt.
The victory was UMBC's first (1-12) of the season and snapped a 13-game overall losing streak. Niagara dropped its fourth straight game and fell to 3-11.
UMBC junior guard Chris De La Rosa (America East Player of the Game) led all scorers with 21 points. Sophomore Adrian Satchell scored a season-high 12 points and added a game-best nine rebounds, while Fry contributed 10 points and eight caroms.
Niagara freshman win Skylar Jones led a balanced Purple Eagle attack with 15 points.
The Purple Eagles had taken a 67-66 lead with 25 seconds to play as Jordan hit two of three free throw attempts after being fouled while attempting a trey. After a UMBC time out, Satchell air-balled a foul-line jumper, but Retriever freshman wing Jamar Wertz leaped well out-of-bounds and saved the ball to Fry, who was fouled by NU's Anthony Nelson on a seven-foot shot attempt.
UMBC was just 1-of-5 from the line before Fry hit the game-winners.
Niagara dominated the early stages of the game, building a 27-11 advantage midway through the first half. UMBC committed nine first-half miscues and Niagara outscored the hosts, 12-0 off turnovers and 9-2 on second-chance points. But De La Rosa hit 3 of 4 from behind the arc to draw UMBC to within 40-30 at intermission.
UMBC reversed all of those trends in the second half and tied the game at 46-all after a 16-6 run eight minutes into the frame. The Retrievers took their first lead as freshman forward Chase Plummer (Elizabeth, N.J./St. Patrick) hit a driving layup with 10:11 remaining.
The Retrievers built the lead to 60-54 with 5:40 to play and 64-59 after consecutive layups by Fry with 2:28 to play. But Niagara's Anthony Nelson (13 points) hit three free throws with 2:12 to go and a layup with 1:38 remaining to tie the score at 64-all.
After Niagara's Kashief Edwards made one of two free throws after corralling an offensive rebound with 52 seconds left, De La Rosa restored a 66-65 lead for UMBC after a 17-foot jumper with 37 seconds to play.
De La Rosa, Fry, Satchell and Plummer dominated the paint in the second half, as UMBC outscored NU, 30-8 in the lane in the second half. UMBC also outscored their guests, 11-1 off turnovers and 14-5 on second-chance points. The Retrievers committed only two second-half turnovers.
UMBC shot 43.9 percent from the floor (29 of 66) and were 7 of 18 from behind the arc. Niagara converted only 7 of 22 shots from the field in the second half and were 20-of-50 for the contest. The Purple Eagles converted 19 of 24 shots from the stripe.
De La Rosa is averaging 19.3 points per game in his last five outings.
UMBC opens America East Conference play as they host Stony Brook on Sunday at 5:00 p.m.