Mary Catherine McCormack is an American actress. She has had leading roles as Justine Appleton on the series Murder One (1995–1997), as Deputy National Security Adviser Kate Harper on The West Wing (2004–2006), as Deputy U.S. Marshal Mary Shannon on In Plain Sight (2008–2012), and as Peggy on the comedy series The Kids Are Alright (2018–2019).

Filmography

• The Pitt — Dr. Linda Conley
• 2025Vicious — Mother
• Heels — Willie Day
• 2020Unpregnant — Debra Clarke
• The L Word: Generation Q — Anne Finley
• 2019Treehouse — Lilith
• 25 Words or Less — Self, Mary McCormack
• For the People — Chloe Daniels
• The Kids Are Alright — Peggy Cleary
• 2017Alien Code — Rebecca
• 2017Drone — Ellen
• Loaded — Casey
• 2017The Crash — Sarah Schwab
• Will & Grace — Janet
• 2016A Country Called Home — Amanda
• 2016An American Girl Story: Maryellen 1955 - Extraordinary Christmas — Kay Larkin
• Angie Tribeca — Abigail Liukin
• Divorce — Kathy DeSantis
• 2014Scooby-Doo! WrestleMania Mystery — Ms. Richards (voice)
• 2013Escape from Polygamy — Leann
• Welcome to the Family — Caroline Yoder
• House of Lies — Denna Altshuler
• Scandal — Lisa Elliot
• 2012Should've Been Romeo — Ellen
• The Newsroom — Molly Levy
• 2012The Unprofessional — Hilary Pfeiffer-Dunne
• In Plain Sight — Mary Shannon
• 20071408 — Lilly Enslin
• 2006For Your Consideration — Pilgrim Woman
• 2006Right at Your Door — Lexi
• 2005Madison — Bonnie McCormick
• Traffic — Carole McKay
• 2003Dickie Roberts: Former Child Star — Grace Finney
• K Street — Maggie Morris
• 2002Full Frontal — Linda
• 2002World Traveler — Margaret
• 2001BigLove — Phoebe
• 2001High Heels and Low Lifes — Frances
• 2001K-PAX — Rachel Powell
• Law & Order: Criminal Intent — Mary Shannon
• 2000East of A — Daphne
• 2000Gun Shy — Gloria Nesstra
• 2000Other Voices — Anna
• 2000The Broken Hearts Club: A Romantic Comedy — Anne
• 1999Getting to Know You — Leila Lee
• 1999Harvest — Agent Becka Anslinger
• 1999Mystery, Alaska — Donna Biebe
• 1999The Big Tease — Monique
• The West Wing — Kate Harper
• 1999True Crime — Michelle Ziegler
• 199854 — New Year's Eve Wife (uncredited)
• 1998Deep Impact — Andrea Baker
• 1998The Alarmist — Sally
• 1997Colin Fitz — Moira
• 1997Fathers' Day — Virginia Farrell (uncredited)
• 1997Murder One: Diary of a Serial Killer — Justine Appleton
• 1997Private Parts — Alison Stern
• 1995Backfire! — Sarah
• Murder One — Justine Appleton
• The Wright Verdicts — Beth Eckhart
• ER — Debbie
• 1994Miracle on 34th Street — Myrna Foy
• The Tonight Show with Jay Leno
• Law & Order — Rickie the Bartender

Appearances as themselves (13)

• 2023National Memorial Day Concert — Self
• 2019Still Laugh-In: The Stars Celebrate — Self
• Chelsea — Self
• Chelsea Does — Herself
• Match Game — Self - Panelist
• To Tell the Truth — Self - Panelist
• Late Night with Jimmy Fallon — Self
• Watch What Happens Live with Andy Cohen — Self - Guest
• The Late Late Show with Craig Ferguson — Self
• Jimmy Kimmel Live! — Self
• The Ellen DeGeneres Show — Self
• The Late Late Show with Craig Kilborn — Self - Guest
• Tony Awards — Self - Nominee