Sexton started off as a coach at Chelsea, before leaving to begin his managerial career at Leyton Orient in 1965. In 1966 he was appointed by Arsenal manager Bertie Mee as the Gunners' first-team coach, but a year later returned to Chelsea to become manager following the departure of Tommy Docherty. He led the club to FA Cup success in 1970 and the European Cup Winners' Cup a year later. Chelsea also reached the League Cup final in 1972, but lost to Stoke City. However, Sexton fell out with several players, including Peter Osgood and Alan Hudson, who were subsequently sold. This, combined with other problems at the club, ensured that Sexton did not come close to repeating his earlier success and early in the 1974–75 season – which ended in Chelsea's relegation – he was dismissed.