Jon Culshaw's radio career began in hospital radio in his home town of Ormskirk, Lancashire, landing his first professional job was at Red Rose Radio in Preston in 1987. He went on to work at Pennine Radio, Radio Wave in Blackpool and Hull's Viking FM, where a receptionist persuaded him to go on stage with his impressions.

In 1993, Culshaw won a talent search run on Steve Wright's Radio One show, beating 8,000 candidates. It led to a job on Spitting Image, voicing about 40 characters, and Culshaw now boasts 350 impersonations, including Ozzy Osbourne, Tom Baker, Russell Crowe and Michael Parkinson.

His big break came when he made national headlines for a 1998 Capital Radio stunt in which he successfully called Downing Street and go through to Prime Minister Tony Blair while pretending to be Tory leader William Hague, and engaged him in a lengthy conversation.

In 2000, he starred in the Radio 4 ensemble series Dead Ringers, and soon became its main star. That year, the programme won the Broadcasting Press Guild Award for Best Radio Programme, and in 2001 scooped the Sony award and the British Comedy Award for best radio comedy. The radio show ran for ten series, plus several specials, then transferred to TV in 2002. Seven series had been made as of 2007.

In 2001-2 Culshaw had a programme on ITV called Alter Ego, in which he interviewed celebrities while simultaneously impersonating them. In early 2004, his own show, The Impressionable Jon Culshaw, was commissioned for ITV One, and in 2005, he was a contestant on Comic Relief does Fame Academy. In 2006, he took over BBC One's long-running Commercial Breakdown show, airing odd and funny adverts from around the world.