Georgia Tech had grabbed a 17-14 lead with 44 seconds remaining in regulation time on Tevin Washington's 10-yard scoring strike to Deon Hill.
But Logan Thomas then marched the Hokies (1-0, 1-0 ACC) 51 yards in six plays to set up a pressure-filled, 41-yard boot by Journell, who had missed a 23-yard attempt earlier in the fourth quarter.
In overtime, Washington tossed an interception on the first possession for the Yellowjackets (0-1, 0-1), but Michael Holmes ripped off an 18-yard run for the Hokies, setting up Journell's game-winner.
Thomas finished 21-of-38 through the air for 230 yards, two TD passes and no interceptions, while Holmes picked up 54 yards on 13 carries.
Washington gained 98 yards with a touchdown and an interception on 10-of-15 passing while rushing for 63 yards on 19 carries for Georgia Tech.