Smith appeared in 37 games during three seasons with the Eagles since being drafted in 2014. He did not make a start and totaled four career sacks. The team waived him earlier this week.
In Seattle, Smith will compete for playing time at strong-side linebacker, and the team will see if he can develop his pass rush. Smith contributed on special teams with the Eagles last year and will have to make an impact there to stick on the Seahawks' 53-man roster.
Smith, 25, was selected 26th overall during the 2014 draft. He had 14.5 sacks during his final season at Louisville.