He will play Sunday against the New Orleans Saints, a source told ESPN's Adam Schefter.
In a corresponding move, the Dolphins waived linebacker Justin March-Lillard.
Timmons had been suspended indefinitely after he went AWOL a day before the team's opener in Week 2 against the Los Angeles Chargers. The Dolphins' Week 1 game against the Tampa Bay Buccaneers was postponed until later in the season because of Hurricane Irma.
The Dolphins located Timmons before the game against the Chargers but made him inactive, snapping his streak of 101 consecutive starts.
Dolphins coach Adam Gase had indicated last week that Timmons could return. Without mentioning Timmons, Gase said, "I would say that you can be forgiven if the right steps are taken."
Gase wouldn't discuss details of Timmons' situation other than to say that it was a personal matter but affected the team, which led to the suspension.
According to the collective bargaining agreement, Miami could have suspended Timmons for a maximum of four games.
Timmons, 31, signed a two-year, $12 million contract with the Dolphins this offseason, leaving the Pittsburgh Steelers after 10 years with the team. CBSSports.com reported Sunday that Timmons made a surprise visit to a Steelers practice during the Dolphins' impromptu bye and told some of his former teammates that he regretted leaving the team in free agency and wanted to return.
Technically a home game, the Dolphins' game against the Saints will be played in London.
ESPN's James Walker contributed to this report.