Martin signed as a free agent and took part in the afternoon practice. He reinforces a position where starter Anthony Fasano had only 31 catches for 331 yards and two touchdowns last season.
In 2008, Martin had similar statistics -- 31 catches for 450 yards and three touchdowns -- while sharing time with Fasano.
Martin was placed on season-ending injured reserve following knee surgery last September, and he was waived in December. He said he was at home in Tennessee and not attracting much attention from NFL teams until the Dolphins called Wednesday.
"I'm feeling great," he said. "My biggest thing now is doing what I can do to hopefully make this team and help this team win."
Martin also played six seasons with Green Bay. He has 152 career receptions for 1,519 yards and 14 touchdowns.