Grambling State (2-5) built a 16-point lead over Tech (4-2), and held on, barely, in McCamish Pavilion.
"Man, what a finish; that's all I can say: what a finish," said first-year Grambling State coach Donte' Jackson. "Somehow, some way we found a way to get lucky and the basketball gods were with us today."
Georgia Tech scrambled back from a 47-31 deficit to lead 61-60 when Jose Alvarado hit his fourth 3-pointer of the second half with 1:01 left in the game.
Many things went wrong for Georgia Tech and right for Grambling State, even though Alvarado scored 20 of his game-high 22 points in the second half.
"This one hurts. We just have to keep our heads up," said Alvarado. "We just have to come out with more energy from the jump."
The visitors from the Southwest Athletic Conference got 14 points each from Ivy Smith Jr. and Axel Mpoyo, and dominated their ACC opponent for about 30 minutes before the Yellow Jackets caught fire. In addition to Alvarado's hot hand, Haywood warmed up and added three 3-pointers in Tech's furious run.
Alvarado expanded Tech's lead to 63-60 with two free throws with 43 seconds to go before Grambling State's Smith hit a pair of free throws with no time having gone off the clock because Tech's Brandon Alston was whistled for a foul on Grambling State's inbounds pass.
Next, Tech senior guard Tadric Jackson, who scored 19 points, went to the free throw line only to miss both shots and leave the score unchanged with 34 seconds remaining.
Jackson on Tuesday night scored a layup as time expired to push Georgia Tech past Northwestern, 52-51.
Trailing 63-62 after Jackson's last miss, Grambling State called timeout, and after working the ball around, Smith drove the right side of the lane. He missed, and Tech center Ben Lammers and Haywood went for the rebound.
The freshman guard tipped the ball into the basket for Grambling State.
After a Tech timeout, the Jackets got off one more shot, but Alvarado missed a runner.
"We had the ball. Just slipped out of Curt's hands. There was no one around him," said Georgia Tech head coach Josh Pastner. "We got lucky on Tuesday and we got unlucky today. That's the thrill of victory and the agony of defeat."
Grambling State: The Tigers closed their seven-game, season-opening road trip in high style with one of the biggest wins in school history.
Georgia Tech: The Yellow Jackets got hot late, especially Alvarado and Haywood, but were dreadful shooting the ball most of the game. They made just 9-of-30 shots in the first half, including 3-of-13 3-pointers.
Lammers, who was named preseason All-ACC, had a team-high nine rebounds and a game-high seven blocked shots, but the 6-foot-10 center - Tech's leading scorer and rebounder this season - scored just four points on 1-of-7 shooting. He hasn't practiced because of a sprained ankle since the Jackets beat Bethune-Cookman on Nov. 19. "More than anything else, we rely on Ben," Pastner said. "Our whole offense and defense is designed through Ben Lammers . . . Our entire coverages and everything, and when he's not playing well . . . it's hard for us."
Georgia Tech sophomore guard Josh Okogie, who led the Jackets in scoring last season with 16.1 points per game, on Friday finished his six-game suspension for receiving benefits impermissible under NCAA rules, but he won't play any time soon. He suffered a compound fracture of his left index finger in a preseason exhibition game Oct. 28, and Pastner said that while the bone has healed nicely, infection worries may sideline Okogie for another four weeks or so.
Grambling State will finally play a home game, after seven on the road, on Monday in hosting Tougalou College (Miss.) - a historically black college established by Christian missionaries for freed slaves around 1871.
Georgia Tech will close out a six-game homestand Sunday with an evening game against Tennessee before the Yellow Jackets play their first true road game, at Wofford, on Wednesday.
Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.