The Nationals recalled Thompson from Triple-A Rochester ahead of Sunday's game in Philadelphia, Bobby Blanco of MASNSports.com reports.
He'll be joining the Washington bullpen as a replacement for Jordan Weems, who was optioned after giving up three earned runs over 2.1 innings of long relief in Saturday's 11-5 loss. Thompson has previously made seven appearances for Washington this season, striking out four over six scoreless innings.