Having played with Brian Auger's Oblivion Express, appearing on the band's first three albums together with future Average White Band drummer Robbie McIntosh, Mullen then joined Kokomo and later toured with the Average White Band.
It was while both musicians were touring the U.S. with AWB in the mid-70s that Mullen met up with tenor saxophone player Dick Morrissey, and throughout the 1980s, he found considerable critical, if not commercial, acclaim as joint leader of the pioneering British jazz funk band Morrissey–Mullen. Record producer Richard Niles, who produced the band's sixth album, It's About Time, would go on to produce three solo albums for Mullen.
He has won many British music awards including "Best Guitar" in the British Telecom Jazz Awards (1994, 1996 and 2000).
Most recently, Jim Mullen has recorded as part of The AllStars a collective of session musicians on their Paul McCartney-produced album All About the Music, alongside special guests Jocelyn Brown, Hamish Stuart and Angelo Starr.
- Things May Come and Things May Go but the Art School Dance Goes on Forever (Harvest SHVL 768) (1970) - Pete Brown's Piblokto!: CD re-release - Repertoire (REP 4407-WY) 1994
- Thousands On A Raft (Harvest SHVL 782) (1970) - Pete Brown's Piblokto: CD re-release - Repertoire (REP 4408-WY) 1994
- The Atlantic Family Live in Montreaux (1977)
- Live' at Ronnie Scott's (1980) - with Mike Carr and Harold Smith
- Good Times and The Blues (1993) - with Dick Morrissey and Mike Carr
- Soundbites (1993)
- Big Blues (1997) - with Jimmy Witherspoon
- jimjam (2000) - with Hamish Stuart
- Burns (2000)
- ...but beautiful - Jim Mullen Helmut Nieberle Sextett, bobtale records (2001)
- Cartoon Capers (2001)
- We Go Back (2001)
- The Mose chronicles: live in London, vol. 2 (2002) - with Mose Allison, Blue Note
- Live in Glasgow - (2003) - with Gary Husband, Mick Hutton and Gareth Williams
- He Never Mentioned Love - Claire Martin (2007)
- All About the Music - The AllStars (2007)
- Smokescreen - The Jim Mullen Organ Trio featuring Stan Sulzmann (2007)