Bigby played in just four games for the Packers last year after having ankle surgery at the beginning of training camp.
The Central Florida product spent the past six seasons with the Packers. He recorded 164 tackles and 10 interceptions in 46 career games.
To clear a spot on the 90-man roster, Seattle released fullback Dorson Boyce. The Seahawks also signed rookie wide receiver Brandon Smith and waived/injured tackle Caz Piurowski.