Boston College was unbeaten, unranked and vastly underrated.
"They said we were 16-point underdogs," Boston College guard Dominic Pressley said. "I don't believe it, and I don't think anyone else does who watched this game.
"It was a war out there, and we matched them point-for-point and elbow-for-elbow to the finish."
The Eagles (11-1 overall and 1-1 in the conference), off to their best start in 27 years, missed two chances to tie the game and force a second overtime.
Reggie Williams protected the Hoyas' two-point lead by stealing the ball from Skip Barry under the Boston College basket with 23 seconds left.
"The toughness and competitiveness made it feel like a postseason game," Williams said.
Georgetown (13-0 and 2-0) turned the ball back over, but Michael Adams' 12-foot jump shot hit the front rim with nine seconds left.
"It was the shot to take. I had penetrated and had the shot. It just didn't go in," said Adams, who scored 20 points. " I think we can play with anybody, but I don't know if we should be ranked. When we were ranked last year, it went to our heads, and we were blown out of the water."
Bill Martin scored 19 points, including two free throws with 1:38 remaining in overtime, to give the Hoyas their winning margin.
Martin hit a jumper at the start of overtime for a 76-74 lead, and Georgetown didn't trail again.
David Wingate added 16 points for the Hoyas, and All-American Patrick Ewing had 15 points, 11 rebounds and 9 blocked shots.