Born in San Jose, CA, Walsh was raised in both California and Tucson, AZ. As a student, Walsh pursued acting and regional theater at the University of Arizona. Soon, she relocated to Chicago where she continued her studies with the renowned Piven Theatre Workshop and, later, the Chicago Shakespeare Repertory. Walsh's theater work in Chicago included starring roles in productions of "Flesh and Blood," "Moon under Miami," "Troilus and Cressida," and "Born Guilty," which she also performed as a radio play on NPR. To further her acting career, Walsh relocated to New York City, where she joined the comedy troupe, Burn Manhattan, honing her comedic skills in a number of off-Broadway plays, including "Flight Courier" and "The Four Twins."Making a transition to the screen, Walsh was first cast in a number of small television roles, including in episodes of "ER" (NBC, 1994-2009), "Homicide: Life on the Street" (NBC, 1993-1999), the short-lived "Swift Justice" (UPN, 1996), and "Law and Order" (NBC, 1990-2010). While still performing theater in Chicago, Walsh branched out to film as well with roles in two independent films, "Normal Life" (1996), and "Henry: Portrait of a Serial Killer" (1998). She also starred as a kleptomaniac in the short film "Peppermills" (1997), which won Best Short Film at the Berlin Film Festival in 1998. Walsh's improvisational comedy training soon helped her land more prominent series regular roles on such comedic series as "The Mike O'Malley Show" (NBC, 1999), "The Norm Show" (ABC, 1999-2001), and "The Mind of the Married Man" (HBO, 2001-02). Walsh was then cast in a recurring role on "The Drew Carey Show" (ABC) in 2001. Donning a fat-suit, she portrayed Drew Carey's girlfriend, Nicki Fifer, a woman struggling with her weight and appearance. Walsh went on to appear in the films "The Family Man" (2000), opposite Nicolas Cage and Tea Leoni; "Under the Tuscan Sun" (2003), as the lesbian lover of future "Grey's Anatomy" co-star Sandra Oh; and "Kicking and Screaming" (2005), a soccer comedy starring Will Ferrell. Walsh also had small roles in the films "After the Sunset" (2004), "One Way to Valhalla" (2005), and the family adventure film "Veritas, Prince of Truth" (2005). Walsh scored her biggest career break to date in 2005 when she was cast in the role of the titian-tressed Dr. Addison Shepherd on ABC's hit series "Grey's Anatomy" (2005-). Originally a guest star slated for five episodes, Walsh's character was brought back by popular demand in a recurring role as Patrick Dempsey's adulterous wife - and the bane of Meredith Grey's (Ellen Pompeo) existence - after her surprise appearance at the end of season one's cliffhanger. Walsh's layered portrayal forced viewers to begrudgingly respect the talented Dr. Shepherd, despite her having broken up one of TV's favorite couples. She was so appealing to fans, that when Shonda Rhimes decided to do a "Grey's" spin-off, she chose Walsh's Dr. Addison as the one character who could conceivably carry over. In 2007, "Private Practice" premiered to impressive ratings. It seemed fans were more than happy to follow Dr. Addison to her new Los Angeles-based private practice as she acclimated to a new city, job and several attractive co-workers, including Taye Diggs, Tim Daly and Paul Adelstein.Walsh returned to movie theaters as one of several terrified customers under siege inside a remote desert diner in the apocalyptic supernatural thriller, "Legion" (2010), starring Paul Bettany as the gun-toting Archangel, Michael. Juggling her continuing "Private Practice" duties with the occasional film venture, the actress appeared alongside the likes of Jeremy Piven, Mira Sorvino and Elizabeth McGovern as members of a tight-knit rural community coping with the death and disappearance of a local child in the indie drama, "Angels Crest" (2011). Walsh next played the mother of a troubled teenage introvert (Logan Lerman) who is befriended by a beautiful and popular classmate (Emma Watson) in writer-director Stephen Chbosky's romantic drama "The Perks of Being a Wallflower" (2012), based on his young-adult novel of the same name. Following the end of "Private Practice" in 2013, Walsh brushed up her comedic chops in the spoof "Scary Movie 5" (2013) and co-starred in Courteney Cox's directorial effort "Just Before I Go" (2014). After appearing in the first season of "Fargo" (FX 2014-), Walsh returned to a starring role on network TV with the sassy comedy "Bad Judge" (NBC 2014-15), in which she played a jurist with a wild side. The series attracted controversy from legal groups who didn't like its portrayal of female judges, but its competitive time slot (up against Rhimes' major hit "Scandal" (ABC 2012-) was the show's undoing, canceled due to poor ratings during its first season.