Nicholas began his pop career as early as 1960. Adopting the stage name Paul Dean, he formed Paul Dean & The Dreamers who were booked to support The Savages, the backing band for the British rocker, Screaming Lord Sutch. It was here that Sutch first noticed the young Nicholas, who was soon to become vocalist and pianist with The Savages.After settling on the stage name Paul Nicholas, Nicholas eventually found success in the UK in musicals, beginning with the leading role of Claude in Hair (which Stigwood produced) before winning the title role in the original London production of Jesus Christ Superstar. The part of Danny to Elaine Paige's Sandy made them the first British couple to play the leads in Grease. He joined The Young Vic under Frank Dunlop and played Claudio in Much Ado About Nothing and appeared in Crete and Sgt. Pepper by John Antrobus. He appeared as the Bully of the Boulevard in Richard O’Brien’s T-Zee at London's Royal Court Theatre. He also performed in Prospect Theatre Company's Carl Davies musical Pilgrim. It was while touring with O'Brien in Hair in 1970 that he first heard songs from the yet to be produced Rocky Horror Show and made the first professional recording with O'Brien singing "That Ain't No Crime". On the b-side was a song entitled "Very 50s", where O'Brien introduces the characters Brad, Janet, and Dr. Scott (In 2005 Nicholas sent O'Brien a CD copy of the recordings with a view to releasing them as an historical record). Thereafter Nicholas returned to the West End starring in Harold Fielding's revival of Charlie Girl with Cyd Charisse.

In 1976, he embarked on a short-lived but high profile pop career. He released the single "Heaven on the 7th Floor" in 1977. This only just reached the UK Top 40, but reached number #1 in New Zealand and #6 on the Billboard Hot 100 listings in the US Paul received a gold record.