After his first season at the Camp Nou, Petit was linked with moves back to England with Manchester United, Tottenham and Chelsea, joining the latter in 2001 in a £7.5 million transfer deal. He initially was a first-team regular for the "Blues" in a largely disappointing first season and played in the 2002 FA Cup final which Chelsea lost to his old club, Arsenal. He scored his first goal for Chelsea in a 2–1 win over Derby on 30 March 2002. His second season saw a significant improvement, as he formed an impressive midfield partnership with Frank Lampard as Chelsea impressed in the winner-takes-all final game of the season against Liverpool as Chelsea secured the fourth UEFA Champions League berth. He also scored twice throughout the season: against Everton in the League Cup, and former club Arsenal in the league. After a series of knee injuries, however, he spent much of his final season of his career on the sidelines, and he was released on a free transfer in the summer of 2004, his final appearance for the club coming against Blackburn Rovers on 1 February 2004.