The team made the move Tuesday, along with signing offensive linemen Allen Barbre and Breno Giacomini. The Seahawks released running back/fullback Quinton Ganther and offensive linemen Mike Gibson and Mansfield Wrotto to make room.
Stokley played in all 16 games last season for Denver, but he had just 19 catches. Two years ago, when Bates was the Broncos' offensive coordinator, Stokley had 49 receptions, second most in his career.
The Seahawks signed the former Packers for offensive line depth, but other help might be on the way. The Tacoma News Tribune reported Tuesday that rookie tackle Russell Okung, the No. 6 overall pick in April's draft, is scheduled to practice Wednesday, and he could be joined by free-agent signee Chester Pitts.
The Associated Press contributed to this report.