The team announced the deal, which Grimes said was a four-year contract.
"It's a four-year deal," Grimes told Josina Anderson of ESPN. "I wanted to be back, but you never know in this business, and when it all worked out I was happy."
There was some speculation that the Dolphins might use the franchise tag on Grimes in advance of Monday's 4 p.m. ET deadline. Grimes himself was "pretty optimistic" that he could work something out with the Dolphins. (Grimes, understandably, didn't want the tag; he was playing on a tag with Atlanta when he suffered his injury.)
Miami signed Grimes to a one-year deal when the Falcons let him walk after a year where he suffered a torn Achilles during the first game of 2012.
The Dolphins then signed Grimes to a one-year, $5.5 million deal and the cornerback played in all 16 games for Miami, recording four interceptions, 16 pass deflections, 60 tackles and scoring a touchdown.
He was an absolute steal for Miami and ironic proof that making it rain in free agency -- which is what the Dolphins did last offseason -- isn't the most prudent way to create a roster.