After retiring from playing, Harris went on to be assistant manager to Venables at Crystal Palace, QPR (helping the team reach the FA Cup Final in 1982 and win promotion to the First Division in 1982–83) and FC Barcelona (winning La Liga in 1984–85 and reaching the 1986 European Cup Final). He also led Egyptian side Al Ahly to the African Cup as Champions from 1993 to 1995.