Florida's Emilio Bonifacio singled in his final at-bat to extend his hitting streak to 25 games.
Javier Vazquez (7-9) allowed a run on six hits and left the game after seven innings owning a 4-1 lead. Cameron then added insurance with a solo shot in the eighth and a two-run blast in the ninth.
That gave Florida enough of a cushion to survive a four-run ninth by the Nationals. Michael Morse drove in the third and fourth runs of the inning with a two-out single, but Leo Nunez then came on to relieve Steve Cishek and got Laynce Nix on a deep fly ball to right to end the game. Nunez recorded his 29th save.
Mike Stanton homered for the Marlins in the first and Nix hit a home run in the fourth to give Washington the only run it managed until the ninth.
Livan Hernandez (5-10) lost to the Marlins for the third time this season, allowing four runs on five hits in four innings.