Texas had a seven-point lead with 2:17 remaining in regulation, but it didn't last. Mississippi State ended the second half on a 7-0 run, Jordan Pope's shot in the closing seconds didn't fall.
The Longhorns never led in overtime, losing to the Bulldogs on Saturday at Moody Center, 101-98.
Dailyn Swain carried Texas (9-5, 0-1 SEC) with 34 points and 14 rebounds before fouling out at the 1:42 mark of the second half. Tramon Mark (20 points, three rebounds, two steals and a blocked shot) and Matas Vokietaitis (19 points and four rebounds) were the other Longhorns who scored in double figures.
Mississippi State (9-5, 1-0) was led by the backcourt duo of Josh Hubbard (38 points, 6-for-17 from 3-point range) and Jayden Epps (27 points, five assists, three rebounds and a steal). Achor Achor (10 points, 13 rebounds and three blocked shots) was the only other player in double figures for Chris Janz's team.
The loss in Sean Miller's first conference game as Texas coach was a game the Longhorns needed to win in their quest to make the NCAA Tournament. Texas is about to go through a brutal three-game stretch with consecutive SEC road games against No. 19 Tennessee on Tuesday and No. 14 Alabama next Saturday before returning home to face No. 11 Vanderbilt on Jan. 14.