Yandle, Frank Vatrano, Colton Sceviour and Derick Brassard scored, and Aaron Ekblad had two assists for Florida (23-22-8), which is 6-2-0 in its past eight games after a seven-game losing streak (0-5-2).
Brett Connolly had two goals and an assist, and Lars Eller had a goal and an assist for Washington (30-18-7), which had won three of four. Braden Holtby made 26 saves.
"It was one of those games where we played well enough to win but we also made enough mistakes to lose," Holtby said.
Washington's Evgeny Kuznetsov tied the game at 4-4 when he scored with 3:06 remaining in the third, but Connolly took a slashing penalty in the offensive zone with four seconds left.
"It's an important time of the game," Connolly said. "It's one of those plays, just a tough position. Teams are too good. You can't take that penalty."