Financial details of the contract, confirmed by a team source and a source close to Willis, were not yet available.
Willis 26, had never started a game before last season. But he played in and started all 16 games for the Seahawks, splitting his time between right guard and right tackle. The '08 season proved to the skeptics that Willis was a prototype power-side blocker, capable of handling either position on a full-time basis.
In his first three seasons, Willis appeared in only six games, including just one appearance in his first two years in Seattle. But injuries and his development as a dependable strong-side blocker moved him into the lineup.
For his career, the former Florida State star and fourth-round pick of Seattle in the 2005 draft, has appeared in just 22 games. But the Seahawks, along with other teams, felt his best football was ahead of him.
It is likely that Willis will move into the lineup at right guard in 2009. But retaining him provides the Seahawks depth and experience on its blocking units.
Seattle might also be planning for the long-term, and the eventual retirement of Pro Bowl left tackle Walter Jones at some point in the not too distant future. When Jones retires, it is expected that current starting right tackle Sean Locklear will move to the left side, opening a spot at right tackle for Willis.
Willis visited in recent weeks with the Washington Redskins and the Oakland Raiders, and several more teams had attempted to line up trips for him. The demand for Willis, though, likely prompted Seattle officials to ramp up their pursuit of him.
Len Pasquarelli is a senior NFL writer for ESPN.com