The agreement Thursday includes $1 million in available performance bonuses for Storen, who was among six extra players eligible for salary arbitration this winter under baseball's new labor deal.
Storen saved 43 games for the Nationals in 2011. He missed more than half of last season after having elbow surgery in April, but reclaimed the closer job for the NL East champions down the stretch and finished 3-1 with a 2.37 ERA and four saves in 37 appearances. The right-hander failed to hold a ninth-inning lead against St. Louis in Game 5 of the NL Division Series.
Washington signed free-agent closer Rafael Soriano to a $28 million, two-year contract this week.