Thomson had a Scottish father and an Irish mother. Her parents split up when she was three and she was brought up in Surrey by her father's parents, who were originally from Alloa. At the age of six, she was sent to a boarding school for five years. Much later she went on record to say boarding schools should be abolished.
She trained as an actress at the Central School of Speech and Drama.
Thomson shared her first lead in Stealing Heaven (1988) with Derek de Lint and Denholm Elliott. In its review, Films and filming said "Kim Thomson's Heloïse moves with delicate poise, a heroine worthy of Rossetti or Burne-Jones, with vivacity and intelligence. The next year, 1989, she played Estella in a film of Great Expectations directed by Kevin Connor, with Jean Simmons, who had played Estella in the 1946 film, as Miss Havisham. Also in 1989 she was Cordelia on stage in King Lear, directed by Jonathan Miller, with the British Theatre Yearbook commenting "Kim Thomson's Cordelia can rarely have been equalled; she was exquisite in beauty, tender in care, full of youthful integrity."
In 1992, Thomson was the leading lady of the TV series Virtual Murder, and in 1994 played another leading role in a costume drama series, The Wanderer. Dozens more appearances in film and on television followed, often as a character actress, such as her role as a society reporter in The Princess Diaries 2: Royal Engagement (2004).
In 1997, she took on the part of Lady Chiltern in An Ideal Husband, of which the Theatre Record said "Others have played this pure, cool, idealistic, demanding role with more authority and finesse, but she is simply right for it". In 2001, she was Irina in a new West End theatre production of Uncle Vanya directed by Peter Gill.
In March 2009, she became a regular cast member of the ITV1 soap opera Emmerdale, playing the role of Faye Lamb. At the end of 2009, she signed a new contract with the show. In January 2011, it was reported that she was leaving the show and would make her on-screen departure later in the year.
In 2010, Thomson graduated from the University of London with a degree in politics, philosophy and history. She canvassed for Barack Obama in Nevada during the presidential election of 2008 and also supported Gordon Brown.
Film and television
- Party Party — Brenda (1983)
- Cover Her Face - Sally Jupp (4 episodes, 1985)
- Lovejoy (1986) "The Firefly Cage" — Nicola Page
- Brush Strokes — Lesley Bainbridge (1986)
- Screamtime - Lady Anne (1986)
- The Life and Loves of a She-Devil — Elsie Flowers (1986)
- Stealing Heaven — Heloise (1988)
- Tales of the Unexpected - Elly (1988)
- The Tall Guy — Cheryl (1989)
- Minder - "Fatal Impression" Sylvie (1989)
- Great Expectations — Estella (1989)
- Jekyll & Hyde - Lucy Harris (1990)
- Perry Mason: The Case of the Desperate Deception — Cathy Bramwell (1990)
- Inspector Morse - "The Sins of the Father" Helen Radford (1990)
- Hands of a Murderer (TV film) - Sophie DeVere (1990)
- Murder 101 — Francesca Lavin (1991)
- The Adventures of Sherlock Holmes (1991) "The Illustrious Client" - Kitty Winter
- Virtual Murder — Samantha Valentine (1992)
- The Wanderer — Beatrice (1994)
- Loved By You — Becky Edwards (1997)
- The 10th Kingdom — Queen Riding Hood III (2000)
- Midsomer Murders — Janet Reason (2001)
- The Princess Diaries 2: Royal Engagement (2004) — Elsie Kentworthy, Reporter
- Rosemary & Thyme (2006) — Andrea
- Secret Diary of a Call Girl (2007) — Della
- 1408 (2007) — Desk Clerk
- Messages (2007) — Frances Beale
- The Street (2007) — Pat Tinsey
- The Bill (2008) — Naomi Woods
- New Tricks (2008) — Tiffany Barker
- The Green Green Grass (2009) — Antonia Page
- Taggart (2009) — Phyllis
- Emmerdale - Faye Lamb (2009–2011)
- Casualty (2009) — Amber
- Holby City (2014) — Catherine O'Malley
|Phoenix Theatre||Alan Bleasdale's Are You Lonesome Tonight?||Priscilla Presley||Robin Lefevre|
|Haymarket Theatre & Old Vic||An Ideal Husband||Lady Chiltern||Peter Hall|
|Old Vic Theatre (1989)||King Lear||Cordelia||Jonathan Miller|
|Theatre Royal, Bath||Present Laughter||Joanna||Dominic Dromgoole|
|Battersea Arts Centre||The Stranger||Madame Y||Michael Billington|
|Battersea Arts Centre||Traveller Without Luggage||Valentine||Nicholas de Jongh|
|Field Day Theatre Company||Uncle Vanya||Elena||Peter Gill|
|Watford Palace Theatre||Wedding Song||Stella||Michael Attenborough|
- "Kim Thomson." Contemporary Theatre, Film and Television. Vol. 76. Gale, 2007, pages 333-335.
- "Kim Thomson". September 29, 2010. Retrieved 2011-04-03.
- Steve Hendry (18 October 2009). "I'm delighted I swapped Hollywood for Emmerdale, says Kim Thomson". The Daily Record. Retrieved 14 November 2010.
I'm Celtic. My father was Scottish, my mother Irish. I was brought up by my dad's parents who have sadly died but were Scots. My family are from Alloa. I love Scotland. I sound so English but I actually didn't realise that until I was older.
- Rick Fulton (1 March 2010). "Emmerdale star Kim Thomson: I've handed out a few slaps since I joined soap.. and received a few". The Daily Record. Retrieved 14 November 2010.
- Films and filming, Issues 413-422 (Hansom Books, 1989), pp. 44-45
- John Glavin, Dickens on Screen, p. 214
- David Lemmon, British Theatre Yearbook 1990, pp. 43-44
- Theatre Record, vol. 17, Issues 9-17 (1997), p. 975
- Plays international, vol. 17 (Chancery Publications Ltd., 2001), p. 9
- Daniel Kilkelly, Kim Thomson to leave 'Emmerdale', dated 30 January 2011, at digitalspy.co.uk, accessed 3 April 2011
- Stanley Wells, Shakespeare Survey Vol. 43 (Cambridge University Press, 2002), p. 194