Sam Houston (8-11, 2-3) led by as many as 16 points in the second half. But, led by Johnathan Jordan with 14 points and Terence Jones with 12, Texas A&M-Corpus Christi (3-15, 2-4) outscored the Bearkats 29-17 in the second half.
Sam Houston was rolling up until halftime, and went into the break shooting 50 percent from the field, while A&M-Corpus Christi shot only 21.4 percent in the period.
Steven Werner led Sam Houston State with 17 points and nine rebounds. Darius Gatson's three-pointer put the Kats up 40-24 with 15:50 to play.
The Bearkats took hold of their 16-point lead on a 3-pointer from Darius Gatson just over four minutes into the second half.
But that was the last time Sam Houston (8-11 overall, 2-3 Southland) would show any signs of a shooting touch. The Islanders went on a 21-9 run, which included a span where Sam Houston went 10 minutes without a field goal.
"The game wasn't won or loss in the last couple of seconds," Bearkats coach Jason Hooten said.
With just under a minute to go, Islanders forward Chris Hawkins-Mast drove the lane and scored to bring A&M-Corpus Christi within two. Then, point guard Johnathan Jordan knocked down a free throw that narrowed the Bearkat lead to one point.
Sam Houston turned the ball over on a shot-clock violation when DeMarcus Gatlin's 3-point attempt fell far short of the rim.
The Islanders called a timeout with five seconds left to draw up a play to win the game, and they did exactly that.
A&M-Corpus Christi put the ball in the hands of the conference's assist leader, Jordan, who was already at his game average of four.
Jordan penetrated and as the Sam Houston defense collapsed on him, Hameed Ali stood wide open in the corner ready for the game-winning basket.
Ali drilled it with just .3 seconds left to spare.
"We figured they were going to help, so we set two shooters in the corner and he (Jordan) made a good pass and it just happened to be me," Ali said. "It feels good because we've definitely been on the other side of this a lot this season. But we just knew Sam Houston was a tough opponent and we had to keep fighting the whole game. We just came out victorious."
Both teams had smaller lineups on the floor on that final possession. Defensively, the Bearkats switched off screens with the bigger players stepping out and helping on the ball.
"We played that last play the way we wanted to," Hooten said. "The guy got by on penetration and we helped over in the gap so he wouldn't get a layup and kicked it out to a guy who is an average shooter at best. Give the kid credit, he stepped and made a huge shot.
"When you do what we did down the stretch and in the last 12 to 14 minutes of the game - you play with fire, you get burned."
A&M-Corpus Christi beat UTSA by the same score as the Saturday number over Sam Houston - 50-49. For of the Islanders six Southland Conference games have been decided by four points or less. In Sam Houston's case, three of its five conference games have been decided by three points or less.
A win would have tied the Bearkats with Stephen F. Austin in the west division. The Lumberjacks, also Sam Houston's next opponent, fell to conference-leader Texas-Arlington Saturday night. Texas Arlington improves its conference record to 6-0, while UTSA also added to the win column Saturday with a road defeat over Texas State to improve the Roadrunners' conference record to 5-1.
Sam Houston and Stephen F. Austin meet on Wednesday in Nacogdoches at 7 p.m. The game will be telecast regionally on the Southland Conference Television Network.