The Aggies led by 14 at halftime, 38-24, but the Cowboys came back to within two points, 50-48, midway through the second half on a 3-point play by Terrel Harris.
Donald Sloan then hit a jumper, got fouled on a 3-point attempt and made all three free throws to put the Aggies comfortably ahead, 55-48..
Texas A&M made 11 free throws in the last five minutes to secure the win.
Texas A&M (17-5, 3-4 Big 12 Conference) had fours players score in double figures, led by Bryan Davis with 18 points. Josh Carter had 17 points and 7 rebounds, Donald Sloan had 15 points, and freshman David Loubeau came off the bench to score 10 points with 4 rebounds.
Oklahoma State (13-7, 2-4), which has lost four of its last five, was led by Terrel Harris with 17 points.
The Aggies, who lost to the Cowboys 72-61 earlier this season, have won two straight and are 13-1 at home this season.
Texas A&M travels to Norman to face No. 4 Oklahoma on Wednesday night.