In his last year in secondary school, he performed Elton John's Daniel in the school's annual show. Simm decided to concentrate on music and joined a local indie band called AnAlien where he began writing his own material. He applied to go on the ITV talent show, Stars in Their Eyes, where he appeared as Simon Fowler of Ocean Colour Scene. After a few years of writing and performing on the northern pubs and clubs circuit, as well as spending a summer season in a band called Force 5 with James Fox, Simm auditioned for the ITV reality TV show, Popstars.
The five runner-up contestants of Popstars formed the group Liberty. The act proceeded to sign a multi-million-pound record contract with Richard Branson's independent record label V2 records. Shortly after forming, Liberty received a legal challenge in the UK High Court from a funk R&B band, also called Liberty, who achieved success in the 1990s. The original Liberty claimed that the newly formed Liberty was taking advantage of the goodwill that had been created by the former's success. The final judgement was in favour of the funk R&B band and the ex-Popstars then asked readers of UK tabloid newspaper, The Sun to suggest a new name. The winning name was "X Liberty", but the group used the entry as the basis for the official title, Liberty X.
Simm, focusing on his solo career, created his own Myspace music profile, uploading demo tracks for his fans to hear his progress as a solo artist. Simm was signed to JamDown Music, where his track Brand New is featured on their official website's music player. On 3 October 2008, Simm's debut album, titled Brand New, was released in Japan. The album has since appeared for purchase on iTunes.
In 2016, Simm auditioned for the fifth series of The Voice UK singing a soulful version of Sia's Chandelier. All four coaches; will.i.am, Ricky Wilson, Boy George and Paloma Faith, turned their chairs for him and he chose to join Faith's team. Simm lost against Faith Nelson in the battle rounds and was nearly eliminated from the competition, but was stolen by Wilson, joining his team for the knockout rounds. He won the knockouts and won the final of The Voice UK. Simm released his UK debut single All You Good Friends shortly afterwards.
In September 2018, the band Wet Wet Wet announced that Kevin Simm was the new singer.He started singing with the band at two shows, St Lukes in Glasgow and The Venue in London in November 2018. Following on from their sold out shows, they then started a nationwide 18 date tour.
