Jackson atoned for a turnover that led to the Black Bearsâ€™ previous score, as Maine's Junior Bernal stole the ball from the Retriever center near mid-court and scored on a driving layup to give his side a 55-54 advantage with 1:12 remaining.
But Bernal missed the ensuing free throw and after UMBC could not convert on two shots on the next possession, Maine's Andrew Rogers missed both free throw attempts with 31 seconds remaining.
The Black Bears trapped UMBC sophomore guard Chris De La Rosa (Washington Heights, N.Y.) in front of the Retriever bench and denied a pass to sophomore wing Chauncey Gilliam (Columbia, Md.). But De La Rosa found a wide-open Jackson on the left baseline and the Retriever center drove and laid in the game-winning shot.
After a time-out, Maine's third-quarter court pass was picked off by UMBC freshman forward Adrian Satchell (Windsor, Conn.) with 0.3 seconds left.
The win was UMBCâ€™s first in the conference this season and snapped Maine's six-game winning streak. Six of Maine's nine wins in a 9-1 streak occurred by six points or less.
Gilliam and freshman Brian Neller (Red Bank, N.J.) led a balanced attack with 12 points each. Satchell, UMBC's America East Player of the Game, recorded his first career double-double with 10 points and a game-high 10 rebounds. De La Rosa contributed eight assists, while Jackson registered all eight of his points and six of seven rebounds in the final 19 minutes.
The Retrievers, who are last in the America East, allowing 74.2 points per game, held Maine to 32.1 percent from the floor and neutralized the Black Bears size advantage by corralling just one less rebound (36-35) than the hosts.
"Our defensive effort was phenomenal today," Head Coach Randy Monroe said. "It's a young group. I am very proud of the guys."
Maine sophomore Gerald McLemore led all scorers with 16 points, but was only 5-of-16 from the floor, often hounded into tough shots by De La Rosa.
After allowing the games first basket, UMBC took a 4-2 lead and led for the entire first half, until Maine's Sean McNally's basket with 14 seconds to play sent the game to halftime tied at 26-all.
UMBC enjoyed one six-point first half lead and five leads of six points in the final 20 minutes. De La Rosa's two free throws with 4:14 remaining gave the guests a 51-45 lead, but back-to-back three's by a tightly-guarded McLemore knotted the game at 51-51 with 2:53 remaining.
Neller hit his fourth three-pointer of the game to restore UMBC's lead at 54-51 with 1:46 remaiing. But two free throws by Maine's Troy Barnies and Bernal's steal and bucket put the hosts in position for the win.
UMBC has now won three straight games at Alfond and four in a row overall against the Black Bears.
The Retrievers have the week off before hosting Vermont on Saturday, Feb. 6 at 3:00 p.m.