Darren Kent added 19 points for the Wildcats (22-11). Dominique Sutton finished with nine points and 12 rebounds, including an offensive grab he put back to tie the game at 73 with four seconds remaining and force the overtime.
Champ Oguchi led Illinois State (24-10) with 23 points but fouled out midway through the overtime with the Redbirds trailing 77-76.
Kansas State seized control of the game in overtime, with a layup by Pullen putting the Wildcats ahead for good at 80-79 with 14 seconds left.
Neither team could establish a lead until a 10-2 Kansas State run gave the Wildcats a 27-20 advantage in the opening period. But a basket by Illinois State's Osiris Eldridge with 5:59 left sparked a 12-4 run to close out the half. The Redbirds held Kansas State to one field goal in the final 6:11 and led 32-31 at the break.