On March 16, 2007, Tate appeared on Comic Relief in the guise of some of her well-known characters from The Catherine Tate Show. Tate appeared as character Lauren Cooper in sketches with David Tennant who acted as Lauren Cooper's teacher and British Prime Minister Tony Blair who saw Lauren Cooper while she was on work experience at 10 Downing Street. Tate also appeared as Elaine Figgis who had met actor Daniel Craig on the internet, as Geordie Georgie with Lenny Henry, and Joannie "Nan" Taylor on an episode of Deal or No Deal hosted by Noel Edmonds.

Tate co-wrote and starred in her own comedy sketch programme called The Catherine Tate Show. Despite speculation that the third series would be the last, Tate and the BBC have not ruled out further series or episodes. In an interview on The Paul O'Grady Show on December 18, 2006 Tate indicated that a fourth series was unlikely but hoped to film a one-off special episode in 2007. She has also indicated that she would be happy to take the show on a live tour.

Tate has been nominated for and won several awards for her work on the show. In 2004, Tate won a British Comedy Award for "Best comedy newcomer" for her work on the first series of The Catherine Tate Show and on December 13, 2006, Tate won a British Comedy Award for "Best British Comedy Actress" for her work in the second series of The Catherine Tate Show. She was also nominated for a BAFTA Award for "best comedy performance" in the second series. Doctor Who

In 2006, Tate appeared in Doctor Who as Donna Noble, a woman in a wedding dress who suddenly appeared in the TARDIS at the end of the episode "Doomsday". She then played a major role as Donna in the Christmas special "The Runaway Bride", the episode which continued from "Doomsday". On her appearance in the series, Tate commented "I was holding out for a summer season at Wigan rep but as a summer job, this'll do."

It was announced on July 4, 2007 that Tate would be returning to Doctor Who to reprise the role of Donna as the Doctor's companion throughout the fourth series of the revived series, due to be shown in 2008. Russell T Davies said: "We are delighted that one of Britain's greatest talents has agreed to join us for the fourth series".

Tate had roles in three films in 2006. These films included; Starter for Ten, Sixty Six and Scenes of a Sexual Nature. She appears in the forthcoming films: Mrs Ratcliffe's Revolution, in which she plays the title character, and Love and Other Disasters.

In 2001 she played Smeraldina in a Royal Shakespeare Company production of A Servant to Two Masters. In 2005, Tate played a role in the West End play Some Girl(s), alongside Friends star David Schwimmer, Sara Powell, Lesley Manville and Saffron Burrows. In an interview Tate commented that she could not look Schwimmer in the eye during her time with him, leading to speculation that the pair did not get on. Tate immediately denied the rumours, explaining that she was joking about her attempts to act "cool" around the actor who she described as "a very funny, personable man, and easy to get along with".

Tate was born in Bloomsbury, London and brought up in the Brunswick Centre. Her mother was a florist. Tate never knew her father as her mother left him very early on in Tate's life. Consequently Tate was brought up in a female dominant environment, and was cared for by her mother, grandmother and her godparents.

Tate attended St Joseph's, Macklin Street, a local Catholic primary school; followed by Notre Dame High School, Southwark, a south London convent secondary school for girls. She studied for A-levels in the sixth form of Salesian College, Battersea, another south London secondary school, before going on to train at the Central School of Speech and Drama. Until the age of 26, Tate lived in Holborn and Bloomsbury.

Tate's partner is stage manager Twig Clark. They have one child, a girl called Erin (born 2003). After giving birth to Erin, Tate suffered from bad postnatal depression. The family currently have a home in Fulham, London.