ESPN's Adam Schefter first reported that Lynch had agreed to a new deal with Seattle. NFL Network's Ian Rapoport has also reported that Lynch's $24 million extension will pay him $12 million next season.
According to Rapoport, Lynch met with team executives in Seattle on Friday, including owner Paul Allen, before signing the deal.
Seattle head coach Pete Carroll has said the team and Lynch were trying to negotiate a contract extension for a while, and conflicting reports had recently emerged over whether the sides had agreed on a deal.
Last season, the 28-year-old Lynch rushed 280 times for 1,306 yards and 13 touchdowns as the Seahawks reached their second consecutive Super Bowl. He also had his most productive receiving season since 2008, catching 37 passes for 367 yards and four touchdowns.
Lynch has spent the last five years with the Seahawks after he was traded by the Buffalo Bills in October 2010.
- Molly Geary