Alexander Semin and Nicklas Backstrom also scored for the Capitals. Washington has won four straight, eight of its last 11 games, and trails the Philadelphia Flyers by two points for the eighth and final post-season spot in the Eastern Conference.
Alex Ovechkin scored an empty-net goal and added a pair of assists in the win for Washington, which also moved within three points of Southeast Division leader Carolina.
J.P. Dumont and Jason Arnott scored for Nashville, which has lost four of its last five games and remained four points behind Vancouver, Calgary and Colorado for the eighth playoff spot in the Western Conference.
Goaltender Dan Ellis started for the Predators but was pulled after he allowed three goals on eight shots in about 14 minutes.