The Dolphins announced the deal Friday on social media. The team also signed veteran cornerback Cre'Von LeBlanc and waived defensive end Nick Coe and long snapper Rex Sunahara.
Griffin, who had his left hand amputated at age 4 because of amniotic band syndrome, joins the Dolphins' roster right before training camp. The signing doesn't guarantee Griffin will make the team's final roster, but it provides him a chance to compete for a depth role.
The 26-year-old Griffin wasn't tendered by the Seahawks as a restricted free agent earlier this year, making him an unrestricted free agent. After visiting with multiple teams this off-season, he opted to join Miami.
Griffin was the first player with just one hand to be drafted in the NFL's modern era when the Seahawks picked him in the fifth round of the 2018 draft. He made the team's roster out of training camp in 2018 and 2019 and was one of the club's top special teams contributors each year.
Over three seasons in Seattle, Griffin appeared in 46 regular-season games and recorded 25 total tackles, one sack and a pass breakup.
Dolphins players are set to report to training camp Tuesday.