| Year | Title | Role | Notes |
| 1995–1996 | Mr. Show with Bob and David | Various Characters | 10 episodes |
| 1996–1998 | The Larry Sanders Show | Mary Lou Collins | 18 episodes |
| 1997 | The Weird Al Show | Weather Woman | Episode: "Talent Show" |
| Over the Top | Linda | Episode: "The Bee Story" |
| 1998 | NewsRadio | Waitress | Episode: "The Secret of Management" |
| 1999 | Tracey Takes On... | Traffic School Girl | Episode: "Lies" |
| Shasta McNasty | Diana | Episode: "Pilot" |
| 1999–2000 | Veronica's Closet | Chloe | 15 episodes |
| 2001 | Just Shoot Me! | Penny | Episode: "Maya Judging Amy" |
| 2002 | Gilmore Girls | Girlfriend in Kirk's film | Episode: "Teach Me Tonight" |
| The King of Queens | Priscilla Stasna | Episode: "Arthur, Spooner" |
| 2003–2010 | 24 | Chloe O'Brian | Main role (season 3-8); 125 episodes |
| 2003 | Good Morning, Miami | Hollis | Episode: "I Second That Promotion" |
| 2004 | Home Movies | Penny (voice) | Episode: "Those Bitches Tried to Cheat Me" |
| 2005 | The Sketch Show | Various Characters | 6 episodes |
| 2006 | Gilmore Girls | Town Troubadour | Episode: "Partings" |
| 2007 | Human Giant | Mindy | 2 episodes |
| The Simpsons | Chloe O'Brian (voice) | Episode: "24 Minutes" |
| 2008 | The Middleman | Dr. Gibbs | Episode: "The Pilot Episode Sanction" |
| 2009 | Flight of the Conchords | Karen | Episode: "Prime Minister" |
| 2009–2023 | It's Always Sunny in Philadelphia | Gail the Snail | 4 episodes |
| 2010 | Royal Pains | Blake | Episode: "Lovesick" |
| The Benson Interruption | Herself | Episode |
| 2010–2013 | Chelsea Lately | Herself | 9 episodes |
| 2011 | Modern Family | Tracy | Episode: "Our Children, Ourselves" |
| Raising Hope | Tanya | Episode: "The Cultish Personality" |
| How to Be a Gentleman | Janet | 9 episodes |
| 2012 | The L.A. Complex | Herself | Episode: "Down in L.A." |
| Dirty Work | Roxy | 3 episodes |
| The Burn with Jeff Ross | Herself | Episode: "Jimmy Kimmel/Jim Norton/Bobby Lee/Mary Lynn Rajskub" |
| Mash Up | Herself | TV movie |
| Grey's Anatomy | Marion Steiner | Episode: "Migration" |
| 2013 | The Mentalist | Susie Hamplin | Episode: "Days of Wine and Roses" |
| Newsreaders | Laney Trammings | Episode: "Fit Town, Fat Town" |
| New Girl | Peg | Episode: "Winston's Birthday" |
| Arrested Development | Heartfire | 2 episodes |
| 2013–2014 | 2 Broke Girls | Bebe | 5 episodes |
| 2014 | TripTank | Marilyn (voice) | Episode: "Crossing the Line" |
| Californication | Goldie | 4 episodes |
| 24: Live Another Day | Chloe O'Brian | 12 episodes (limited series) |
| Talking Dead | Herself | Episode: "Four Walls and a Roof" |
| 2014–2017 | @midnight | Herself | 15 episodes |
| 2015 | Maron | Herself | Episode: "Ex-Pod" |
| 2015–2016 | Brooklyn Nine-Nine | Genevieve Mirren-Carter | 5 episodes |
| 2015 | Highston | Jean Liggetts | Pilot |
| W/ Bob & David | Chef Krissie | Episode |
| 2016 | The Girlfriend Experience | Erin Roberts | 10 episodes |
| Take My Wife | Mary Lynn | Episode: "Opener" |
| Those Who Can't | Summer | 3 episodes |
