The Wildcats trailed 65-58 with 4:02 to go before McIntyre scored on a layup and then made a 3-pointer to get Kansas State within two.
After Texas' Annissa Hastings made two free throws, Kendra Wecker scored for the Wildcats and Megan Mahoney made a 15-footer as the shot-clock expired to tie the score at 67-all. Texas then committed a shot-clock violation and Wecker hit a turnaround jumper to give Kansas State its first lead of the game.
McIntyre added two free throws to extend the Wildcats' lead to 71-67 with 26.9 seconds to go. Tiffany Jackson scored on a post move, and Kansas State's Laurie Koehn made one of two foul shots for the winning margin.
Daria Mieloszynska and Jamie Carey missed potential game-tying 3s in the final seconds.
Wecker finished with 17 points for the Wildcats, who outscored Texas 14-4 over the final 4 minutes. Brie Madden added 14 points and Mahoney had 11.
Jackson had 24 points and nine rebounds for Texas (21-8), which has never beaten Kansas State in the Big 12 tournament. Carey hit four 3-pointers and finished with 19 points.
The Longhorns opened the game with a 17-0 run. Kansas State missed its first nine shots and committed six turnovers as Texas moved to the early lead.
Wecker finally got the Wildcats on the scoreboard with 14:16 to go in the half, and Kansas State began to whittle away at its deficit. McIntyre drained a deep 3-pointer with 1:33 to go in the half, getting Kansas State within 34-27.
Kansas State got within 40-34 with 15:25 to play when Wecker scored in the post and converted the three-point play, but Texas countered with an 11-2 run for a 51-36 lead with 12 minutes left.