Warren Hills stunned Chatham 52-46 in double overtime in the North 2, Group III title game on Tuesday.
Colin McKenna scored 16 points, Jack Rooney had 15 points and Tristan LeMon added 13 for the Cougars.
Chatham finishes its season at 28-2. The Cougars are the last Morris County team to be active in the state tournament.
The Cougars thrilled a raucous home crowd early on by taking a 17-6 first quarter lead. The Blue Streaks cut the deficit to 23-16 at halftime.
Warren Hills used an 11-0 run and briefly took the lead with 1:15 left in the third quarter. A pair of McKenna free throws gave Chatham a 28-27 lead going into the fourth quarter.
Warren Hills rallied and took the lead late in the game but McKenna hit a layup late to force the first overtime period.
Strong play by Rooney gave Chatham a 5-point lead late in the first overtime but Warren Hills rallied to tie the game at 42.
Warren Hills took the lead in the second overtime and knocked down free throws late to win its first state sectional boys basketball title in school history.