Ryan Rossiter scored 12 of his 19 points in the second half and had 13 rebounds as Siena stunned Georgia Tech for the second time in program history, 62-57 on Wednesday night.
Entering the game, the Saints (4-6) considered their 76-68 win over the Yellow Jackets in the 1994 NIT to be their greatest home win.
Rossiter had his 40th double-double despite a sickness requiring two IVs before the game and a blow to the face late in the first half that sent him to the locker room for medical attention.
Siena used a 15-2 second-half run to turn a six-point deficit into a 49-44 lead with 9:51 to play.
Georgia Tech (6-5) tied the game twice, but never regained the lead in the homecoming of coach Paul Hewitt, who left Siena for the Yellow Jackets in 2000.
The Saints hit 6 of 8 free throws in the final 38 seconds.
Glen Rice paced Georgia Tech with 15 points.