"Awesome to see 2 great guys working together- my 2 longtime friends John Schneider top client Ryan Grigson working together with the @Seahawks," agent Buddy Baker posted on Twitter later Tuesday night.
Grigson served as a senior personnel executive with the Cleveland Browns last season before being dismissed after John Dorsey replaced Sashi Brown as the team's general manager.
The 46-year-old Grigson, who replaced Pro Football Hall of Famer Bill Polian in 2012, was fired from the Colts in January 2017.
Grigson's first draft was highlighted with the selection of quarterback Andrew Luck with the No. 1 overall pick in 2012.
The Colts went 11-5 and reached the playoffs in 2012, and Grigson was named the NFL's Executive of the Year.
Grigson, however, was also responsible for the team trading a first-round pick for Trent Richardson. The Colts released the running back two years later.