Kate Walsh was born in San Jose, California, on October 13, 1967. She grew up partly in San Jose and partly in Tucson, Arizona, later attending the University of Arizona, where she got involved in regional theater. She later moved to Chicago where she began working with the Piven Theatre Workshop and, later, the Chicago Shakespeare Repertory. She performed on National Public Radio in the production of the radio play "Born Guilty". Walsh later moved to New York City and joined the comedy troupe "Burn Manhattan", performing in a number of Off-Broadway plays.

Her first major television appearance came on The Drew Carey Show where she portrayed Niki Fifer, Drew's girlfriend and a woman struggling with her weight. She 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 Norm. She continued to appear on television programs in supporting or bit parts.
Attended University of Arizona Wore a fat suit in her role as Nicki Fifer on The Drew Carey Show. Grew up in San Jose, California and Tucson, Arizona. Often compared to Catherine Deneuve, an icon of French cinema. So much so that it was written into an episode of Grey's Anatomy where a patient's husband becomes fascinated with Walsh's character because of the resemblance. Was a runway model in Japan during the early 1980s. The Japanese were fascinated by her size and height (5' 10"). Portrayed the girlfriend of her future Grey's Anatomy cast mate, Sandra Oh, in Under the Tuscan Sun. Coincidentally, her character in the film was also a doctor. The film, The Sweetest Thing, was written by Kate's best friend, Nancy Pimental. The film's female characters were based on Nancy and Kate. Also, Kate can be seen on the DVD's special features. Mother is Italian. Wore glasses as a child. Good friend of Jamie Denbo, Sara Morris, Cynthia True and Sally Ann Brooks. Attended Catalina High school in Tucson, Arizona. Engaged to Alex Young, a production co-president at 20th Century Fox [May 16, 2007]. Ranked #52 on the Maxim magazine Hot 100 of 2007 list. First leading role was with co-star Wes Bentley in the New York Indy production of Three Below Zero, which won the Max Ophüls award 1999 fort best picture in Germany.