Terms of the deal were not disclosed by the team, although the NFL Network reported that Blount agreed to a one-year contract worth $4.5 million.
The 31-year-old Blount will be reunited with new Lions coach Matt Patricia, who served as the defensive coordinator during the sledgehammer back's tenure in New England.
Last season, Blount rushed for 766 yards and two touchdowns on 173 carries. He led the NFL with 18 rushing touchdowns while churning out a career-best 1,161 yards with the Patriots in 2016.
In eight seasons with the Tampa Bay Buccaneers, Pittsburgh Steelers, Patriots and Eagles, Blount ran for 5,888 yards and 51 touchdowns in 116 games. He also rushed for 600 yards and 11 TDs in 11 postseason games.