Tim Firth was born in Frodsham, England. He spent much of his time at school writing songs and it was only a few weeks before going to Cambridge to read English that he attended an Arvon Foundation course in West Yorkshire. This was run by Willy Russell and whilst on it, Firth had to write dialogue. He wrote about the only thing he knew - two sixteen-year-olds trying to write a song. Another course participant optioned it for his production company and Firth decided to become a writer. While at Cambridge he joined the Footlights where his contemporaries included David Baddiel who later invited him to contribute music to The Mary Whitehouse Experience on BBC radio. His first plays at this time were all directed by Sam Mendes.

On leaving Cambridge, he wrote and composed music for the award winning Radio Four series And Now In Colour but was soon invited to meet Alan Ayckbourn in Scarborough and commissioned to write a play for the studio at the Stephen Joseph Theatre. His one-act play A Man Of Letters was a success and led to the commissioning of a full-length play from Ayckbourn, Neville's Island, which later transferred to the West End, has been seen in translation all round the world and has been in almost continuous production since its premiere. It was revived in the West End in 2013 at the Duke of York's Theatre.

Along with his father, Gordon Firth, he created a children's audiobook for WHSmith and EMI which he would later turn into the TV series Roger and the Rotten Trolls, running for four series' and winning a BAFTA. The spin off series Ripley and Scuff also won a BAFTA, and more recently the Radio Times voted the original series one of the [1]50 Greatest Children's TV Shows of All Time.

During two successive Christmas runs, the stage version of his TV film The Flint Street Nativity at the Liverpool Playhouse became the most successful Christmas production in the theatre's history.

His play Calendar Girls, adapted by Firth from his own film, found favor with audiences across the UK during its 2008/09 tour, and in the process broke the all time British box office record for a play and also continued to sell out during its West End residency. In 2010, the hit comedy embarked on a UK country wide tour and has since been produced worldwide.

In 2004, Firth became a Companion of The Liverpool Institute for Performing Arts.

In March 2010, Firth was awarded an honorary Doctor of Letters, honoris causa by the University of Chester.[5]