On December 28, 2018, it was announced that Williams would be retiring after 13 seasons and his last NFL game would be on December 30, 2018 against the Miami Dolphins. In the game Williams made three tackles on defense, one for a loss. In what ended up being the final play of his NFL career, he lined up as an extra fullback on offense and caught a pass, advancing the ball nine yards. In another offensive play that game, Williams served as a lead blocker on a Josh Allen touchdown run. After the season, Williams was named to his sixth Pro Bowl, replacing an injured Jurrell Casey.