Terms of the contract were not made official, but various outlets reported it to be a one-year deal.
Garrard, 34, took to Twitter to confirm the signing: "It's official guys I'm a Miami dolphin!!! Couldn't be happier!!!"
The nine-year veteran sat out the entire 2011 campaign. He was cut by Jacksonville prior to the season, then underwent back surgery and was not picked up by another team.
In 86 career games -- all with the Jaguars -- Garrard has thrown for 16,003 yards and 89 touchdowns against 54 interceptions while rushing for 1,746 yards and 17 scores.