Kevin Shattenkirk scored a power-play goal 3:13 into overtime to give the Capitals a 3-2 win over the Penguins in Game Three of their East semifinal in Pittsburgh.
Evgeni Malkin and Justin Schultz scored 48 seconds apart late in the third period to tie the game at two for Pittsburgh.
Nicklas Backstrom and Evgeny Kuznetsov had staked Washington to a 2-0 lead.
Pittsburgh star Sidney Crosby left the game after being injured on a hit by Matt Niskanen, who was given a game misconduct for the infraction.
The Pens now lead the series 2-1 and host Game Four tomorrow night.