Pettit left the game with LSU holding an 8-1, but the Gators made things interesting with four runs in the bottom of the ninth against reliever Jake Tompkins.
LSU (35-17, 16-10) becomes the first team to win a series at Florida this season and has won nine of its last eleven games. The Tigers secured a berth in the Southeastern Conference Tournament with Friday's win against the Gators, but they cannot capture the overall SEC title after Alabama earned a win against Mississippi State on Sunday.
LSU hosts Alabama in the final SEC series of the year next weekend.
While Pettit held Florida (37-15, 17-10) to five hits, LSU logged 13 against Gators' starter Keith Ramsey who had pitched a two-hitter and one-hitter in his previous starts.
The decisive hit for LSU was a three-run homer from pinch hitter Matt Heath in the eighth inning that gave the Tigers a 7-1 lead. After an 0-for-4 performance against his former team in Saturday's game, Heath was benched in favor of Jon Zeringue in left field.
With runners on first and second with one out, Heath sent an offering from reliever Kevin Coleman over the right field fence to plate the eventual winning runs.
Heath was the first batter Coleman faced after replacing Tommy Boss, who walked the first batter he faced, Chris Phillips, on four straight pitches. Ramsey was pulled for Boss after giving up a one-out single to David Raymer.
Florida also had a pinch hitter take the ball out of the park. Matt Maley's one-out homer against Tompkins with one out in the ninth made the score 8-2.
Following the homer, the Gators drew back-to-back walks and added two runs on a double and a single. A throwing error on J.C. Holt on the single allowed another Florida run to score, cutting LSU's lead to 8-5, but Pettit got the next two Florida batters to fly out to end the game.
Walks got Pettit in trouble in the first inning when he totaled 45 pitches. A bases-loaded pass to Kevin Sobieraj gave Florida a 1-0 lead in its first at-bat.
LSU evened the game with an RBI single from Wally Pontiff in the third inning and took the lead on a sacrifice fly from Phillips in the fourth. Sean Barker made the score 3-1 with a run-scoring single in fifth inning.
Phillips finished off a strong weekend with an RBI-double to center field in the sixth inning for a 4-1 LSU lead.
The final LSU run came in the ninth on a fielding error charged to Kiger, the Florida shortstop, that allowed Barker to score from second on a grounder from Jason Columbus.