Thomas is from Georgia Military College and will have three years of eligibility to play at U of L. He will battle with Kyle Bolin, Reggie Bonnafon and Brett Nelson for the backup spot.
"I'm pleased that Patrick has joined our program," Petrino said. "He is a dual-threat quarterback who adds depth to that position heading into the fall. Patrick is talented and I'm excited to add him to the mix as we head into the ACC this season."
In one season at Georgia Military, Thomas passed for 1,695 yards and 17 touchdowns and helped his team to the JUCO national title. He also ran for 199 yards and two more TDs.
Thomas originally signed at UAB in December with former head coach Garrick McGee, who is now the offensive coordinator at Louisville.