Williams walked into the Dolphins' locker room at 3 p.m. on Monday, shortly after signing his contract and the locker room erupted with celebration.
"I'm excited to be back with my brothers," said Williams, who sat out the first five games of the NFL season.
The former USC standout, who the Tennessee Titans selected in the third round of the 2010 draft, caught four passes for 100 yards in the Dolphins' exhibition season. He caught a 54-yard pass from Matt Moore in the exhibition win over the Dallas Cowboys.
Brandon Gibson sat out Monday's practice, and it is possible his unknown injury could sideline him a week or two, which might explain Williams return.
Williams also served as a punt returner during his Dolphins tenure, and it is possible he could push Jarvis Landry for that role. Landry, a rookie from LSU, has struggled fielding punts this season, gaining 51 yards on nine returns.
The Dolphins presently have an extra roster spot because of Derrick Shelby's suspension, but the team will need to release a player later this week to make room for safety Reshad Jones, who returned from his four game suspension.