With the win, Texas State (11-10, 5-7 Sun Belt) has swept the season series and owns the tie-breaker on South Alabama (7-16, 5-7).
Nearly a third of the Bobcats' made field goals (23) were 3-pointers as they hit eight from long range. They made a season-high 10 in their first meeting with South Alabama.
The Jaguars scored a season-low in points, held to 31-percent shooting (16-52), making just 4 of 16 from 3-point range and 7 of 12 from the line. Texas State's defensive stopper Wes Davis was back in the lineup after injury.
Ken Williams led the Jaguars with nine points on 3 of 12 shooting.
JaMarcus Weatherspoon added 12 points for Texas State, which scored the first seven points and led by 18 at halftime.