| Year | Title | Role | Notes |
| 1994 | The House of Eliott | Charlotte Parker | Guest role, series 3, episode 1 |
| 1995 | Six Pairs of Pants | Various characters | |
| Tears Before Bedtime | Maggie | |
| Crown Prosecutor | Jackie South | |
| 1996 | Mash and Peas | Various roles | |
| Asylum | Martha & Nurse McFadden | |
| 1996–1997 | Staying Alive | Alice Timpson | |
| 1997 | Midsomer Murders | Judith Lessiter | Episode: "The Killings at Badger's Drift" |
| Armstrong and Miller | Various roles | Series 2, episode 1 |
| Harry Enfield and Chums | | Episode: "Harry Enfield and His Yule Log Chums" |
| 1998 | Unnatural Acts | Various roles | Main cast |
| Alexei Sayle’s Merry-Go-Round | Alice, the Ayatollah's Assistant | Episode 1 |
| 1998–2010 | The Royle Family | Cheryl Carroll | Recurring role |
| 1999 | People Like Us | Sarah | Episode: "The Estate Agent" |
| 1999–2001 | Spaced | Daisy Steiner | Also co-wrote with Simon Pegg |
| 2001 | Randall & Hopkirk | Felia Siderova | Episodes: "Mental Apparition Disorder", "Drop Dead" |
| Bob & Rose | Holly Vance | |
| Comedy Lab | Wife | Episode: "Knife & Wife" |
| 2002 | Dick Whittington | The Good Fairy | Television film |
| Black Books | Eva | Episode: "Hello Sun" |
| 2005 | According to Bex | Rebecca 'Bex' Atwell | |
| 2006 | Pinochet in Suburbia | Police Guard | Television film |
| The Secret Policeman's Ball | Mrs. Peacock | Recording of staged show |
| QI | Herself | Episode: "Domesticity" |
| Agatha Christie's Marple | Aimee Griffith | Episode: "The Moving Finger" |
| 2007 | Doctor Who | Nurse Joan Redfern | Episodes: "Human Nature", "The Family of Blood" |
| Learners | Beverly | Television film |
| Never Mind the Buzzcocks | Herself | Series 21, episode 1 |
| 2010 | Doctor Who | Verity Newman | Episode: "The End of Time, Part Two" |
| Lizzie and Sarah | Various roles | Television pilot |
| 2011–2012 | Twenty Twelve | Siobhan Sharpe | Main cast, won RTS Best Comedy Performance award |
| 2011 | Skins | Crystal | Episode: "Everyone" |
| The Hour | Jane Kish | Episode 4 |
| 2012 | One Night | Carol | |
| World's Most Dangerous Roads | Herself | Episode 2 |
| 2013 | Blandings | Daphne Littlewood | |
| Up the Women | Margaret | Also writer |
| Crackanory | Storyteller | Read "My Former Self" by Holly Walsh |
| 2014 | Alan Davies: As Yet Untitled | Herself | Episode 2 |
| 2014–2017 | W1A | Siobhan Sharpe | |
| 2015 | Celebrity Squares | Herself | Series 2, episode 2 |
| 8 Out of 10 Cats Does Countdown | Herself | |
| 2016 | The Keith Lemon Sketch Show | Manager | Series 2: "The Cartoon Job Centre" sketch |
| Jack and Dean of All Trades | Marv | Web series |
| Hooten & the Lady | Ella Bond | |
| 2017 | The Crystal Maze | The Knight | |
| 2018–2020, 2023 | There She Goes | Emily Yates | Main cast |
| 2019 | Years and Years | Edith Lyons | |
| 2022 | Mood | Laura | |
