The first series of British television sketch comedy The Catherine Tate Show premiered on BBC Two on 16 February 2004. It consists of six episodes and concluded on 22 March 2004. In the first series audiences are introduced to various characters portrayed by Catherine Tate, including Joannie 'Nan' Taylor, Lauren Cooper and Bernie, the Irish nurse. The series was entirely written by Tate alongside Mathew Horne, Derren Litten, Aschlin Ditta, Arthur Mathews and Bruce Mackinnon.

The series premiered in the United States on 27 November 2004 on an unknown network and concluded on 21 February 2005.

Series one is the recipient of a BAFTA Award, British Comedy Award, and a Banff Rockie Award. It has received several nominations including a BAFTA Award, a British Comedy Award, a Royal Television Society Award and an International Emmy Award.

• Joannie 'Nan' Taylor: The foul-mouthed grandmother is an old East London woman who constantly swears at and criticises other people. She is always visited by her well-mannered grandson Jamie, where the visits usually start off well enough, with the Nan showing how grateful she is that her grandson has come to see her. However, things usually take a turn for the worse after she starts to make unfavourable comments about her neighbours, family, and home help visitors. Jamie is a university student, but according to Nan, is unemployed. Nan repeatedly asserts that he is gay, although Jamie has said on many occasions that he has a girlfriend. Regular performances by Catherine Tate and Mathew Horne.
• Lauren Cooper: Lauren Cooper is a comprehensive school student with a bad attitude who is most widely known for her phrase "Am I bovvered?". Lauren, her best friend Lisa 'Liese' Jackson and her love interest Ryan Perkins are known as yobs. Regular performances by Catherine Tate, Mathew Horne and Niky Wardley.
• Bernie: The incompetent Irish nurse. Bernie is an unruly, randy woman who bordered on being sacked in the hospital where she worked in every episode. She frequently makes inappropriate remarks to her patients, flirts with most of the male staff, takes a critically ill patient on a wild night out, and mixes up the records of living patients with those of deceased ones. Regular performance by Catherine Tate.
• Paul and Sam: The Essex couple. They are happily married yet slightly simple, and find everyday situations surprisingly hilarious. Paul and Sam often excitedly tell each other stories, which they find highly amusing and interesting. The stories build up and when completed, Paul and Sam would both produce an exaggerated and completely silent laugh. Regular performances by Catherine Tate and Lee Ross.
• Kate and Ellen: This sketch follows two office workers who sit next to each other. While Ellen is usually keen to get on with her work, she is frequently disturbed by Kate (Tate). Kate continually makes conversation about her lifestyle, inviting her co-worker to "Have a guess!" on such delicate situations. While Ellen is reluctant to go along with the guessing games, she is pressured into making a wild guess, which almost always results in Kate becoming insulted and consequently offensive. Ellen occasionally guesses correctly, causing Kate to become angry and verbally or physically abusive towards her. Regular performances by Catherine Tate and Ella Kenion.
• Elaine Figgis: Elaine is a woman who appears in a documentary following her search for love, mostly corresponding with men around the world via the Internet. The unseen interviewer and narrator called Tanya follows her engagement and eventual marriage to a convicted cannibal and lunatic on Death Row in the US, who abducted, tortured and murdered eight people, proceeding to eat two of them. Regular performance by Catherine Tate and Rebecca Front as the voice of Tanya.
• The Aga Saga Woman: An upper-middle-class woman who goes into a state of shock in various, seemingly innocuous situations. Regular performance by Catherine Tate.

• Am I Bovvered: The Catherine Tate Show Scripts (2 October 2006 - Fourth Estate, ISBN 978-0007242184)^[7]
• Catherine Tate: Laugh It Up! (6 October 2008 - Andre Deutsch Ltd, ISBN 978-0233002590) by Tina Ogle.^[8]