Redskins coach Mike Shanahan previously had said he hoped to sign Stallworth, who suffered serious burns in a hot air balloon accident three months ago. Shanahan also said he was more concerned about the high-ankle sprain Stallworth suffered last season with the New England Patriots, rather than the injuries from the balloon accident.
"I'm beyond grateful and excited to sign with the @Redskins today ... One of best organizations and fan bases in all of sports!" Stallworth wrote on Twitter.
Stallworth, 32, took part in the Redskins' Tuesday minicamp practice as a tryout player.
Stallworth, who had played with the Redskins in 2011, appeared in only one game with the Patriots before the ankle injury ended his season. He has 35 career touchdown catches.
He was suspended for the 2009 season after a car he was driving struck and killed a pedestrian in South Florida that March. He spent 24 days in jail for a DUI manslaughter conviction.
Information from The Associated Press was used in this report.