Cordero will earn $4.15 million instead of the $3.65 million the Nationals offered. Cordero, who was 7-4 with a 3.19 ERA and 29 saves last season and led the Majors with a franchise-record 47 saves in 2005, made $525,000 last season.
The Nationals' record in arbitration cases this year is 1-1. Right-hander John Patterson lost his case last week and will make $850,000.
Outfielders Alex Escobar, Austin Kearns and Chris Snelling and second baseman Felipe Lopez were arbitration eligible, but the Nationals were able to sign them before they reached arbitration.
The hearing was in Phoenix on Tuesday, the final day for arbitration sessions.
"I'm glad to see it all over now," Cordero told The Associated Press. "I can concentrate on the game a lot more and not have to worry about that."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.