While still in high school, Gambaccini began contributing to comics fanzines, including the publication Rocket’s Blast Comicollector. In 1964 he succeeded Jerry Bails (the so-called “father of comic book fandom”) as executive secretary of the Academy of Comic-Book Fans and Collectors, an umbrella organization for the burgeoning world of comics fandom. As part of his involvement with the academy, Gambaccini helped organize the comics industry’s first awards, the Alley Awards.

Born in the Bronx, New York City, Gambaccini studied at Dartmouth College, where he obtained a degree in history in 1970.

Having left Oxford, Gambaccini considered further study in law at Harvard or Yale, but had the opportunity of writing for Rolling Stone magazine, as British correspondent. He attributes his broadcasting career to this post—especially an interview in 1973 with Elton John which brought him to the attention of BBC Radio producer John Walters who arranged for him to host on BBC Radio 1.

Gambaccini then started broadcasting in the UK, on BBC Radio 1, September 1974, which he did for 13 years, first as a music reporter on the John Peel Saturday show Rockspeak. He presented the series All American Heroes from 1974, a series showcasing US talent. In September 1975 he began the show he was to front for the next 11 years, highlighting the weeks’ music in the US chart. The show was broadcast every Saturday afternoon until his last show on February 8, 1986. Thereafter, he moved to independent radio to host American Countdown. In 1990, he returned to Radio 1, but left during the tenure of controller Matthew Bannister in 1993.

Gambaccini and television presenter Jonathan Ross co-owned Top 10 Comics, a comic shop in London which opened in 1989 and closed in 1995. Gambaccini has been an official guest at many British comic conventions, including the United Kingdom Comic Art Convention (where he co-presented the 1990 Eagle Awards and the 1997 National Comics Awards), and Comics Festival UK.

In 1992 Gambaccini became a founding personality on the UK’s classical music station Classic FM, where he hosted the weekly Classical CD Chart show. He left for BBC Radio 3 in 1995, where he broadcast an hour-long morning show, in a slot formerly used for Composer of the Week. He returned to Classic FM in 1997.

Gambaccini has been a supporter of gay-related charities. In 1995, he was named Philanthropist of the Year by the National Charity Fundraisers for his work on behalf of the Terrence Higgins Trust. He is a patron of the London Gay Symphony Orchestra. In 2010, he won an episode of celebrity Mastermind, with his chosen beneficiary charity being Stonewall.

In 1998, he joined BBC Radio 2. His first show was on April 18, 1998, once again opening the first of his weekly shows America’s Greatest Hits with “Born to Run” by Bruce Springsteen. In 2002, he quit his role at Classic FM, to present a weekly chart show on London’s Jazz FM until 2004. He was also a contributor to the London station LBC when it was taken over by Chrysalis.

Gambaccini was co-author of The Guinness Book of British Hit Singles and related titles, with Tim and Jo Rice, alongside Radio 1 colleague at that time, Mike Read, between 1977 and 1996. Gambaccini’s own books include Love Letters, Radio Boy, Top 100 Albums and Track Records. The Ultimate Man, a musical about a comic book superhero, was co-written with Alastair King and Jane Edith Wilson, and produced at the Bridewell Theatre in London in 2000.

In August 2008, Gambaccini returned to Classic FM, to present a 12-part series Paul Gambaccini’s Hall of Heroes on Sunday evenings between 9:00 and 10:00. In March 2008, he took over as chairman of the Radio 4 music quiz Counterpoint from Edward Seckerson; he was temporarily replaced in 2013 by Russell Davies and returned to the show in November 2014 after being cleared of allegations of historical sexual offences made against him. He returned to Radio 2 with America’s Greatest Hits on November 15, 2014 and hosted it until July 2, 2016 when he took over Pick of the Pops from Tony Blackburn, the following week. He started his final America’s Greatest Hits on the BBC with “Born to Run” by Bruce Springsteen and ended it with Justin Timberlake.. The show was revived on Greatest Hits Radio from February 2020 airing 5-7pm on Saturdays, on his first show he began with Born to Run by Bruce Springsteen & the E Street Band & ended his first show with Uptight (Everything’s Alright) by Stevie Wonder.

He then migrated to the United Kingdom and attended University College, Oxford, where he read for a degree in politics, philosophy and economics. He has since returned to Oxford, where he delivered a series of lectures in January and February 2009, as the News International Visiting Professor of Broadcast Media. In February 2010 he was invited by the Vice-Chancellor of Oxford University, Andrew Hamilton to deliver the inaugural LGBT lecture Out on Monday to the university’s LGBT staff, students and faculty.

Gambaccini has always been openly gay, asserting in 2013: “I was never ‘in’.” In June 2012, he entered into a civil partnership with Christopher Sherwood. One week later, they married in New York Botanical Garden.

On 1 November 2013, it was reported that Gambaccini had been arrested on suspicion of historical sexual offences as part of an investigation by Operation Yewtree in the United Kingdom. He was released on bail and his spokesman said that he denied the allegations. It was announced on 10 October 2014 that no charges would be brought. Giving evidence to the House of Commons Home Affairs Select Committee on 3 March 2015, Gambaccini said he believed he was used as human “fly paper” to encourage other people to come forward and make allegations against him.

In 2013, Gambaccini claimed that he had been highlighted as a potential security risk by the BBC earlier in his career due to his sexuality, with a symbol resembling a Christmas tree on the cover of his personnel file: “It meant you were ‘as camp as Christmas’ and thus a potential security risk.” In fact, the symbol was a general indication that the subject should not be “promoted or transferred” without reference to the department responsible for security vetting, due to left-leaning sympathies.

The BBC reported that he also “said he suspected his bail was repeatedly extended until the end of high-profile cases involving other celebrities because police did not want juries to hear a former Radio 1 DJ had been cleared of sexual wrongdoing”. Gambaccini also argued in favour of a 28-day bail limit; Home Secretary Theresa May had announced in December 2014 that she was consulting on such a limit in all but exceptional cases. However, Gambaccini’s allegations of a “witch-hunt” were denied by Keir Starmer, the Director of Public Prosecutions (DPP). The 28-day limit came into effect in April 2017.

Gambaccini wrote an account of his experience in his book Love, Paul Gambaccini: My Year Under the Yewtree, which was published in 2015. In February 2016, the Irish Supreme Court Judge Adrian Hardiman used a review of this book to criticize what he described as the radical undermining of the presumption of innocence, especially in sex cases, including Gambaccini’s case, by the methods used in Operation Yewtree (among other instances).

In February 2017, Gambaccini sued the Metropolitan Police, citing a loss of £200,000 during his time under investigation. In November 2018, he settled a claim against the Crown Prosecution Service, who agreed to pay him damages; the amount paid to Gambaccini by the CPS was not disclosed due to confidentiality clauses in the settlement agreement.