Kathy Burke was born at The Royal Free Hospital in London to Irish immigrant parents. As a child she attended the Maria Fidelis RC Convent School.

Burke's first acting role was in the controversial film Scrubbers, directed by Swedish actress Mai Zetterling and featuring Pam St. Clement, Robbie Coltrane, Miriam Margolyes, Honey Bane, Debby Bishop and Eva Mottley. The movie was set in a young offenders' institute for girls and was seen as a female version of the infamous Scum.

Burke first became familiar to television audiences as a player of minor roles in sketches by better-known performers such as Harry Enfield, Dawn French and Jennifer Saunders.

Along with French & Saunders, she has contributed to two Comic Relief charity singles. She first appeared as a member of Bananarama parody band Lananeeneenoonoo in 1989, and then as a member of Spice Girls' lookalike band The Sugar Lumps in 1997.

In real life Burke is a big fan of Morrissey and appeared in the video for his 1989 single "Ouija Board, Ouija Board" and later in the 2002 Channel 4 documentary The Importance Of Being Morrissey.

She quickly became successful in her own right and although mainly associated with comedy, she has played several serious roles including that of Queen Mary I of England in Elizabeth.

In 1997 Burke won the Best Actress award at the Cannes Film Festival for her role in the gritty drama Nil by Mouth. Since then she has appeared as Perry in Kevin and Perry Go Large, and as Linda La Hughes in Gimme Gimme Gimme. In 2000 She appeared in the cult film Love Honour and Obey with Ray Burdis.

In 2003, she was listed in The Observer as one of the 50 funniest acts in British comedy.

Since 2001 she has refrained from acting and has thrown herself into theatre directing; something she considers to be one of her true passions. She said in an interview with Dawn French in Dawn French's Girls Who do Comedy that she no longer felt the same creative energy associated with acting that she used to (she described it as a "feeling in my belly") and that this was the reason she had stopped acting. However, she has done some voiceover work in the past few years, including adverts for Ski yoghurt (in the UK) as well as Flushed Away (2006). She also appeared in the 2007 Christmas Special of The Catherine Tate Show as Nan's daughter.