Sam Houston (8-10, SLC 2-2) led by seven, 70-63, with 2:35 to play after a layup by Steven Werner.
Texas State (8-9, SLC 1-3) cut the margin to 70-68 in the next 15 seconds on a layup by Reid Koenen and a three-pointer by Eddie Rios.
But the Bearkat defense held the Bobcats scoreless the rest of the way while adding a point on a free throw by Marquel McKinney with six seconds left. Vonn Jones missed a three point shot for Texas State at the buzzer.
Sam Houston outscored the Bobcats 36-26 in the paint, out-rebounding Texas State 35-30. Steven Werner led the Kats with nine rebounds. Staff pulled down eight boards.
The game was reminiscent of the loss to Texas-San Antonio 10 days earlier in the first Southland Conference game of the season when Sam Houston let a six-point lead with three minutes to go slip away on a last-possession shot.
But the outcome was a bit different against Texas State, which came into Johnson Coliseum as a Southland Conference opponent for the last time before leaving for the Western Athletic Conference next season.
The Bearkats sent their longtime rivals away with a 71-68 loss in front of a crowd of more than 1,300 on the first day of the spring semester.
"The UTSA game prepared us for a close game," said sophomore DeMarcus Gatlin, who led the Bearkats with 19 points.
There was room for error for Sam Houston, which similar to the game against UTSA, held a seven-point advantage with three and a half minutes left to play.
"As a team, we knew adversity would hit," senior Marcus James said. "So as a team, we just tried to keep everybody on the same page and keep everybody going in the same direction. We knew they were going to make a run and we would try to withstand it to win the game."
Texas State made its runs throughout the night, every time the Bearkats gained momentum.
Late in the game, it was all about Bobcats guard Eddie Rios, a transfer from Miami who scored 14 of his 18 points in the second half and torched Sam Houston from the perimeter.
The Bearkats bent, but never broke and never relinquished their second-half lead.
"It's good to see we responded to adversity because that's what we've kind of faced all year long and what we've been about," Sam Houston coach Jason Hooten said. "Really, that game there, to be honest is the same game as the UTSA game."
Sam Houston led by five points at halftime on 52 percent shooting Wednesday, while holding Texas State to 36 percent shooting.
The second half was a different story. The Bearkats shot 46 percent from the field, while allowing the Bobcats to shoot 58 percent. Much of that had to do with Rios, who made all six of his shots in the second half.
Hooten noted what was important for the Bearkats was getting to the foul line and knocking down free throws. That's what Sam Houston did in the second half, by attempting just as many free throws in that period as Texas State did for the entire game.
Sam Houston went 10-for-17 from the foul line in the second half, while the Bobcats shot only 2-for-5 from the line.
James contributed 18 points and five rebounds for Sam Houston. Konner Tucker, who came off the bench for matchup purposes, added 10 points.
Sam Houston's Steven Werner led the rebounding battle with a game-high nine rebounds, four of those on the offensive end and one big board that came inside a minute to play.
Senior Antuan Bootle scored on both of his field goal attempts, while Michael Holyfield played limited minutes, also for matchup purposes.
With the win, the Bearkats improve their conference record to 2-2, and 8-10 overall.
Sam Houston hosts Texas A&M-Corpus Christi on Saturday at 7 p.m. The Islanders are coming off a 77-73 loss to Texas-Arlington Wednesday night.