Maloney was born in Peckham, London, to Irish parents, and began boxing at school. After attempts to become a Catholic priest, jockey and professional footballer, Maloney became a chef but continued to box and began training other boxers and organising amateur contests. By the late 1970s this had led to a career as a professional trainer, working with promoter Frank Warren.
After splitting with Warren in the 1980s, Maloney moved into management and began promoting professional fights, becoming Lennox Lewis's manager in 1989.
While known as the promoter who took Lennox Lewis to the top, Maloney has also guided four other fighters to World Titles and has managed a string of British, European and Commonwealth Champions. In 2009, the 'Boxing Binman', Rendall Munroe, made his fifth successive defence of his European Super Bantamweight title and later thrice fought for a world title, twice on an interim basis, drawing once and losing twice.
On 14 September 2009 Maloney suffered a heart attack while watching John McDermott lose a contentious decision to Tyson Fury; significant heart damage was discovered when Maloney was admitted to hospital with shock after finding the body of boxer friend Darren Sutherland. It was reported that Maloney was not welcome at Sutherland's funeral service, although reports circulated that her wife, Tracey, and mother, Maureen, attended.
Maloney announced the decision to retire from boxing in October 2013.
In April 2015 Maloney announced that, following the completion of her gender reassignment, she will be returning to boxing to promote again.
In the London mayoral election in 2004, Maloney was the UKIP candidate and was criticised for comments about lesbian and gay people. These included the explanation that a failure to campaign in Camden was because there were "too many gays". Maloney later attempted to justify these remarks, telling the BBC "I don't want to campaign around gays...I don't think they do a lot for society...what I have a problem with is them openly flaunting their sexuality." James Davenport, chairman of Gay Conservatives, called for Maloney's resignation as a UKIP candidate, saying "Frank Maloney is a dangerous extremist and should resign or be sacked as UKIP's candidate for London mayor. UKIP must back or sack their homophobic candidate."
Maloney was accused of "Griffin-like racism" during the 2004 London Mayoral Elections, and was described as a "dangerous racist". The UKIP campaign manager, Gary Cartwright, a National Democrats candidate and organiser prior to joining UKIP, was a regular contributor to holocaust denier David Irving's historical revisionist Focal Point website. Ken Livingstone, in response to Maloney's campaign, stated that "UKIP are the British National Party in suits."
In an interview with LGBTQ magazine EQView, Maloney addressed her previous statements, stating "I accept comments I made in the past were wrong. If you knew Frank Maloney, if you were there when I made those remarks – you would have seen the smirk on my face. I knew it was wrong but I was saying it in jest [...] it was a mistake."
Maloney was married for over 15 years to second wife Tracey; they have two daughters. Maloney has a daughter from her first marriage and is a supporter of Millwall Football Club. Maloney said in her first televised interview as an open trans woman that she and Tracey are now divorced, but that she has been "very supportive". In 2015, Maloney admitted to nearly having strangled Tracey ten years prior, stating that it was caused by a combination of pent-up frustration, anguish over her gender identity, and alcohol consumption.
In August 2014, Maloney announced publicly that she is now known as Kellie, and is undergoing gender reassignment. Lennox Lewis was initially shocked at the news but expressed respect for Maloney's decision. On a radio interview she discussed her family's reaction with her mother Maureen.
Maloney had already received counselling, hormone therapy, and voice coaching. She had stated that final sex reassignment surgery was set for early 2015. In April 2015, Maloney announced that her gender reassignment was now complete.