Illinois (7-1) led 60-48 before Georgia Tech (6-3) began its comeback. Marcus Georges-Hunt's drive with 1:48 remaining tied the game at 60-all. Daniel Miller's layup with 21 seconds remaining gave Georgia Tech a 65-64 lead.
Illinois forward Joseph Bertrand, who had 10 points, missed a jumper and Georgia Tech's Robert Carter Jr. sank two free throws with three seconds remaining.
Carter led Georgia Tech with 21 points and nine rebounds. Georges-Hunt had 20 points.
Rayvonte Rice scored 24 points, including 13 in the second half, to lead Illinois.
Georgia Tech became the first team to score more than 63 points against the Illini this season.
The Yellow Jackets led 36-33 at halftime after trailing by nine points in the first half.
Rice scored eight unanswered points early in the second half as the Illini reclaimed the lead. He started the run with a free throw before hitting a 3-pointer, and then scoring off his steal.
The Illini stretched the lead to double figures at 60-48 with a 9-0 run midway through the second half.
Georgia Tech avenged a loss at Illinois in last year's Big Ten/ACC Challenge. Rice, a junior transfer from Drake, is the first player to score in double figures in his first eight games at Illinois since Kiwane Garris opened his career with 10 straight games of 10 or more points in the 1993-94 season.
The Illini made 5 of their first 10 3-pointers and led 26-17 before Georges-Hunt led the Yellow Jackets to a 9-0 run to tie the game. Georgia Tech missed its first five 3-points before making its final three long-distance attempts.
Solomon Poole's 3-pointer gave the Yellow Jackets their first lead at 31-28, and Carter added a 3 and a dunk for the halftime lead.