Adams suffered a fractured left index finger on June 15, when he was hit by a pitch, and has missed Washington's last 16 games. He is batting .275 with 13 home runs and 36 RBIs in 57 games this season, his first with the Nationals.
The Nationals announced the move before Wednesday morning's game against the Boston Red Sox. The left-handed-hitting Adams was not in Washington's starting lineup against Boston left-hander Eduardo Rodriguez.
The Nationals designated left-hander Tim Collins for assignment to create a roster spot for Adams. Collins posted a 2.77 ERA in 17 relief appearances for Washington.