Tadric Jackson led Georgia Tech (16-13, 7-9) with 20 points, and Josh Okogie had 14 points and 10 rebounds. The Yellow Jackets have lost three of four.
Josh Heath's jumper with four seconds left pulled Georgia Tech to 62-60, but Farrell made two free throws for the final margin.
Notre Dame struggled to shoot over Georgia Tech's zone defense, going 10 of 29 from 3-point range while being outscored 38-16 in the paint by the Yellow Jackets.
Okogie scored nine points in the first six minutes of the game, but Colson got hot for the Irish not long after. Colson scored seven straight, including his second 3-pointer of the half and a pair of offensive putbacks, and the Irish took a 34-28 lead into halftime.
Beachem's 3-pointer early in the second half gave Notre Dame nine-point lead, but the Irish missed their next seven shots. After Tech cut it to four in that stretch, Colson was there with another 3-pointer to give the Irish some breathing room.
Georgia Tech again cut it to four after back-to-back Jackson drives with five minutes to play, but Farrell bailed the Irish out this time, hitting a desperation fallaway jumper from the corner just before the shot clock expired.
Georgia Tech won the first meeting on Jan. 28, 62-60 on Okogie's buzzer-beating layup. That was the second of what would be four straight losses for the Irish before they turned things around.
Georgia Tech: The Yellow Jackets fell to 1-6 on the road in the ACC and have to win their last two games to finish with a conference record of .500, a mark they haven't reached since going 8-8 in 2007.
Notre Dame: After a week off following a road win at N.C. State, the Irish kept pace with Florida State and Louisville for second place in the league behind North Carolina.
Georgia Tech: The Yellow Jackets host Pittsburgh on Tuesday and travel to Syracuse for their final regular-season game Saturday.
Notre Dame: The Irish host Boston College on Wednesday before closing out the regular season at No. 7 Louisville on Saturday.