Paul Maurice of the Panthers became the fourth coach to reach 1,700 NHL games (Scotty Bowman, 2,141; Barry Trotz, 1,812; Joel Quenneville, 1,768).
John Carlson had a goal and an assist for the Capitals (7-9-2), who have lost seven of nine (2-5-2). Darcy Kuemper made 38 saves.
"I thought we played hard in the last 40 minutes and pushed to get that win," said Washington coach Peter Laviolette, who returned after missing two games while in NHL COVID-19 protocol. "We couldn't seem to get ahead of the score. We couldn't seem to get where we wanted to go."
The teams met for the first time since the Panthers eliminated the Capitals in six games in the 2022 Eastern Conference First Round.
Washington was 0-for-5 on the power play; Florida was 1-for-1.
"I think the penalty kill deserves all the credit for tonight's win," Maurice said. "And the goalie is the key piece, right? Your best penalty killer. They were great."