[3] In 1959, at The 2i's Coffee Bar, he met Marty Wilde and was invited to become a member of his backing group, the Wildcats, who were the opening act in the television series, Oh Boy!, produced by Jack Good.

He was often referred to as "Big Jim" both for his physical appearance and as he was usually first choice to play guitar on sessions for major musicians and bands.

He played on the first records in the UK to use a wah-wah effect – Michael Cox's 1961 "Sweet Little Sixteen" and Dave Berry's 1964 hit "The Crying Game" used a DeArmond Tone and Volume pedal.

[citation needed] In the early 1960s he also played on hits by The Rolling Stones, Marianne Faithfull, Billy Fury, Frank Ifield, Adam Faith, Frankie Vaughan, Helen Shapiro, Johnny Hallyday, Freddie and the Dreamers, Cilla Black, Tom Jones, Shirley Bassey, Dusty Springfield, and others.

[citation needed] Later in the 1960s and 1970s, Sullivan continued to play on a succession of hit records including those by The Walker Brothers, Jonathan King, Donovan, Cat Stevens, David Bowie (he played banjo, guitar and sitar on Bowie's first album which was published in 1967), Benny Hill, The New Seekers, Thunderclap Newman, Love Affair, Long John Baldry, Marmalade, Small Faces, and Rolf Harris.

[citation needed] In the 1960s, Sullivan learned to play the sitar, having been inspired by attending a recording session for Indian classical musician Vilayat Khan.

[citation needed] Throughout this period, Sullivan studied formally with Nazir Jairazbhoy and, until 1969, he all but abandoned guitar in favour of the sitar.

[7] Together with Harrison, Brian Jones of the Rolling Stones and Shawn Phillips, he was among the most dedicated of the many rock guitarists who embraced the instrument during the 1960s.

He released an instrumental album Sullivan Plays O'Sullivan (1971) and was also featured giving guitar lessons on the Bay City Rollers' TV series Shang A Lang.

He fronted a band called Tiger, alongside vocalist Nicky Moore, releasing three albums under this name before the group split up in 1976.