Washington, DC – Chris Kunitz scored the go-ahead goal early 1, at Verizon Center.
Craig Adams found the back of the net in the first period for Pittsburgh, which got 16 saves from Marc-Andre Fleury.
The Penguins have won four of their last six games.
Jason Chimera had the lone goal for the Capitals, who have lost four games in a row, including their second straight under new head coach Dale Hunter. Washington has dropped eight of 10 overall.
Tomas Vokoun made 33 saves in defeat.