Hearn made two layups for the Wildcats when they opened the second half with an 11-1 run. Northwestern (7-2) barely hung on after building an 18-point lead.
Baylor (5-3) was within 70-67 when Pierre Jackson made two free throws with 23 seconds left after a midcourt turnover by Northwestern on an inbound pass. Dave Sobolewski made a free throw with 17 seconds left after Northwestern had missed six free throws in a row.
Jackson had 18 points to lead Baylor, which lost its second home game in a row.
Drew Crawford had 19 points for Northwestern.