The Seahawks acknowledged the deal on Wednesday but wouldn't release terms.
Duckett, who played for the Detroit Lions last season, has 2,642 career rushing yards and 36 touchdowns. When he wasn't slowed by injuries, Duckett was productive in limited opportunities in Detroit's pass-happy offense. Last season, he carried the ball 65 times for 335 yards.
How Duckett fits with the Seahawks will have to be determined. Seattle has recommitted to improving its running game this offseason, signing former Carolina Pro Bowl guard Mike Wahle and hiring former Kansas City offensive line coach Mike Solari as offensive line coach.
Both moves were made in the hopes of sparking a running game that has significantly fallen off since Shaun Alexander was the league MVP after rushing for 1,880 yards and 27 rushing touchdowns in leading Seattle to the Super Bowl in 2005.
Seattle averaged just 4.0 yards per carry in 2006 and 3.8 last season. The struggles have been most notable in short-yardage situations. That's where Duckett's bullying running style could help. But he is likely to be stuck behind Alexander and Maurice Morris on the Seahawks' depth chart unless additional changes are coming.
Duckett previously played for the Washington Redskins and Atlanta Falcons, who selected him 18th overall in the 2002 draft after running for 3,379 yards at Michigan State. His best season came in 2003 when he rushed for 779 yards and 11 touchdowns with the Falcons.
Also Tuesday, Seattle hired former Michigan offensive coordinator Mike DeBord as an offensive assistant and signed tight end Jeb Putzier.
DeBord spent the last two years as offensive coordinator at Michigan under Lloyd Carr, who stepped down after last season. DeBord spent 27 years total coaching in college, including 12 years at Michigan. He was also head coach at Central Michigan for four years.
Putzier played two seasons with the Houston Texans and before that spent four years with the Denver Broncos. Last year, he played in eight games, and had six catches for 39 yards and a touchdown. Putzier has played in 61 career games and has 96 catches for 1,251 yards and three scores.