Halak is set to become an unrestricted free agent on July 1. He made $4.5 million last season.
Halak appeared in 12 games with the Caps, winning five games with a 2.31 GAA and .930 save percentage. He was fourth in the NHL with five shutouts.
Halak had a 24-9-4 record and 2.23 goals-against average with the St. Louis Blues before being shipped to the Buffalo Sabres on Feb. 28. Halak did not play for the Sabres, who traded him to the Capitals a week later.
Washington's newly-acquired fourth-round pick originally belonged to the Blackhawks. Chicago sent that pick to the Islanders in February, in exchange for Pierre-Marc Bouchard and Peter Regin.