The seventh-seeded Seawolves (25-7) advanced to the second round of the NIT and will play at Iowa on Friday night.
"It was a great win for us," Stony Brook coach Steve Pikeill said. "I'm real proud. This is a good basketball team. We deserve to keep playing. I'm proud we're going to get the opportunity to stay in this tournament."
The Seawolves got their 13th road win of the season, tops in the nation.
"I think it's our preparation," said senior captain Tommy Brenton. "We're confident going into every game."
The second-seeded Minutemen (21-12) led 25-21 with 7:05 left in the first half, but they didn't score again in the half. Brenton was on the receiving end of a hard illegal screen foul that knocked him to the ground right before the run. The play seemed to fire up the visitors.
"I like hitting people and I like being hit. Physicality is part of my game," Brenton said. That definitely fired me up personally and I hope our team fed off it."
Stony Brook scored the final 17 points of the opening half to take a 38-25 lead at the break, and controlled the game the rest of the way.
"We were focused at halftime," Jackson said. "We knew the game wasn't over. We all had the best approach coming into the second half."
UMass cut its deficit to at 42-36 quickly in the second half and kept the Seawolves within striking distance for the early part of the half. But Stony Brook scored six straight points to stretch its edge to 63-51 with 4:34 left to seal the win.
"We made big shots when we needed to," Pikiell said. "We're a pretty good basketball team. We have a lot of players who can play. We were well prepared. I thought we executed out game plan."
UMass leading scorer Chaz Williams was slowed by foul trouble in the first half and a shoulder injury fighting through a screen early in the second. He finished with two points and six assists.
"I thought we got beat by a team that was better than us this evening," UMass coach Derek Kellogg said. "They executed their game plan very well. They seemed more energized and quicker to the ball. I was a little disappointed that we didn't have a little more scrap and toughness and fight. That could be attributed to their great defense and them making some really good plays and shots."