| Year | Title | Role | Notes |
|---|---|---|---|
| 1995 | New York News | N/A | Episode: « Cost of Living » |
| 1996 | Swift Justice | Annie Peters | Episode: « Out on a Limb » |
| 1996 | Voice from the Grave | Terry Deveroux | Television film |
| 1996 | Two Mothers for Zachary | Nancy | |
| 1997 | Spin City | Veronica | Episode: « Kiss Me, Stupid » |
| 1997 | Heart Full of Rain | Susan Doyle | Television film |
| 2001 | Big Apple | Sarah Day | 8 episodes |
| 2003 | Out of Order | Danni | 6 episodes |
| 2004–2006 | Deadwood | Joanie Stubbs | 33 episodes Nominated — Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Drama Series |
| 2006 | Numb3rs | Crystal Hoyle | 2 episodes |
| 2006–2009 | Lost | Cassidy Phillips | 4 episodes |
| 2008 | 12 Miles of Bad Road | Jonelle Shakespeare | 6 episodes |
| 2008 | 1% | Rhonda | Unsold television pilot |
| 2008–2009 | Friday Night Lights | Shelby Saracen | 11 episodes |
| 2009 | FlashForward | Kate Stark | Episode: « 137 Sekunden » |
| 2010 | Reviving Ophelia | Le Anne | Television film |
| 2010–2013 | Treme | Janette Desautel | 36 episodes; Main role (seasons 1–4) |
| 2013 | Second Sight | Samantha Wilde | Unsold television pilot |
| 2013–2014 | Sons of Anarchy | Colette Jane | 7 episodes |
| 2013 | White Collar | Jill | Episode: « Quantico Closure » |
| 2014 | Red Zone | Helen Weller | Unsold television pilot[22] |
| 2015–2017 | House of Cards | Kate Baldwin | 9 episodes |
| 2015–2018; 2022–present | Fear the Walking Dead | Madison Clark | 42 episodes; Main role (seasons 1–4) Nominated — Saturn Award for Best Actress on Television (2016)[23] Nominated — Saturn Award for Best Actress on Television (2017)[24] |
| 2016–2018; 2021 | Talking Dead | Herself | 8 episodes |
| 2019 | Deadwood: The Movie | Joanie Stubbs | Television film |
| 2020 | Briarpatch | Eve Raytek | Main role |
| 2025 | The Better Sister | détective Nancy Guidry | season 1 (8ep) 29 may on Prime |