The Falcons, already eliminated from playoff contention, clearly relished their role as potential spoilers in Tampa Bay, where Atlanta quarterback Kirk Cousins threw for 373 yards and three touchdowns - all to tight end Kyle Pitts Sr.
Bijan Robinson also ran for a touchdown and Gonzalez kicked a 43-yarder to seal the victory.
Trailing 28-14 with 13:34 remaining, the Falcons had touchdowns by Robinson and Pitts but missed two-point conversions on both.
After the Bucs, leading 28-26, came up empty on their final drive the Falcons got the ball back and despite a sack of Cousins and a holding penalty set Gonzalez up for the game-winner.
"If you're a pro football player you're a fighter," Cousins said.
"There's a lot for us to play for in terms of just us men and wanting to be excellent at what we do. And I think that showed tonight."
Tampa Bay quarterback Baker Mayfield threw for 277 yards and two touchdowns with one interception.
The Bucs, who had raced to a 6-2 record and threatened to run away with the division, have now lost five of their last six games - including a loss to division stragglers New Orleans last week.
The Carolina Panthers can tighten their grip on the NFC South when they visit the Saints on Sunday.
The Buccaneers and Panthers will then meet twice over the final three weeks of the regular season.
"This one's going to haunt me," said Mayfield, who was particularly stung by a fourth-quarter interception. "This falls on my shoulders.
"You can't turn the ball over, can't have that interception... we have to be better on offense, and it comes down to how I play."
