Gardner-Johnson entered 2021 as a starting safety. He started seven games before being placed on injured reserve on November 13. He was activated on December 11. In a game at the Tampa Bay Buccaneers on December 19, 2021, Gardner-Johnson intercepted Tom Brady's pass intended for Scotty Miller late in the game to close out the 9–0 shutout victory. He finished the 2021 season with two sacks, 46 total tackles, three interceptions, and seven passes defended.
