Television roles
After playing Cathy Buxton in the Homicide: Life on the Street episode "Stakeout" in 1996 and Navy Lieutenant Kirstin Blair in the Law & Order episode "Navy Blues," Walsh's first major television appearance was in 1997, when she appeared on The Drew Carey Show as Drew Carey's love interest, Nicki Fifer. She wore a fatsuit in some episodes of the show.
Walsh went on to portray Carol Nelson in HBO's The Mind of the Married Man television series, and played Norm Macdonald's romantic interest in the sitcom The Norm Show. She made a guest appearance on CSI: Crime Scene Investigation as Mimosa, a transgender woman. She sometimes appeared in sketches on Late Night with Conan O'Brien.
Walsh had a recurring role on Karen Sisco as Detective Marley Novak in 2003 and 2004. In 2005, she was cast in her breakout role in the ABC series Grey's Anatomy, as Dr. Addison Montgomery, the estranged spouse of Derek Shepherd ("Dr. McDreamy," played by Patrick Dempsey). In February 2007, her Grey's Anatomy character received a spin-off of Grey's Anatomy that began airing in September 2007. Taye Diggs, Tim Daly, Amy Brenneman, Chris Lowell, and Audra McDonald were cast in the spin-off, Private Practice. Walsh would return for six episodes across the fourth through eighth seasons of Grey's Anatomy, including the musical episode "Song Beneath the Song."
On June 12, 2012, Walsh announced that the sixth season of Private Practice would be her final season. However, she mentioned she'd be open to reprise her role in Grey's Anatomy for a few guest spots.
In 2013, Walsh appeared in Full Circle, a 10-episode ensemble drama series created by Neil LaBute and airing on DirecTV's Audience Network channel.
In 2014, Walsh had a supporting role in the first season of FX's television series Fargo. She had a guest starring role in Hulu's original series The Hotwives of Orlando and later starred in the NBC series Bad Judge, which aired for one season. From 2017 to 2019, Walsh starred in the Netflix drama series 13 Reasons Why, as the mother of a child who dies by suicide. Her performance was met with critical acclaim, having been dubbed the "best work" of her career.
In 2019 and 2020, Walsh had a significant recurring role as "the Handler" in the Netflix series The Umbrella Academy. Her most recent role has been on Netflix Original, Emily in Paris, where she plays Emily's boss who gets pregnant and can no longer move to Paris for their marketing job, so she sends Emily instead. In September 2021, Walsh announced she would be reprising her role as Dr. Addison Montgomery in the eighteenth season of Grey's Anatomy in a guest starring role.
In 2026, it was announced that Walsh would play the lead role in CBS sitcom pilot The Tillbrooks.
