The veteran free agent linebacker announced on Twitter on Friday: "Redskins fans your captain is back!"
"Excited about returning to the Skins! The support I've received from the fans didn't go unnoticed!" Fletcher later tweeted.
Fletcher, who turns 37 next month, has been the anchor of Washington's defense for five seasons. He's never missed a game in his NFL career, having played in 224 straight since debuting with the St. Louis Rams in 1998.
The Associated Press contributed to this report.