Richardson agreed to a one-year deal, according to multiple media outlets.
A Pro Bowl selection in 2014 while with the New York Jets, Richardson started all 15 games for the Seattle Seahawks this past season. He recorded one sack, one forced fumble, two fumble recoveries and 44 total tackles in 2017.
Richardson, 27, played his first five NFL seasons with the Jets after being their first-round pick in the 2013 NFL Draft.
The Seahawks acquired Richardson in a September 2017 trade with the Jets that sent wide receiver Jermaine Kearse and a second-round pick to the Jets.
Richardson has started 71 of 73 career games.