Courtney Thorne-Smith was born on 8th November 1967 in San Francisco, California. Thorne-Smith's father, Walter, and mother, Laura, divorced when she was 7 and she spent time living with both parents. Thorne-Smith went to school at Menlo-Atherton High School. While in high-school Thorne-Smith performed with the Ensemble Theatre Company.

Thorne-Smith made her on-screen debut in David Seltzer's 1986 film Lucas. The movie featured so other up-and-coming stars like Corey Haim, Charlie Sheen, Jeremy Piven and Winona Ryder. Thorne-Smith followed this performance with roles in teen movies such as Summer School (1987), Revenge of the Nerds II : Nerds in Paradise (1987) and Side Out (1990).

Courtney Thorne-Smith main break through's came by her television work. In the mid-80's, she appeared in the TV shows Growing Pains, Fast Times and Day by Day. Courtney also performed in the TV movies Thanksgiving Promise and Infidelity.

In 1990, Thorne-Smith landed the role of Kimberly Dugan in the hit TV show LA Law, she appeared in six episodes. Courtney's first major TV role came in the Fox prime time soap opera, Melrose Place, where she played the alcoholic Allison Parker from 1992-1997, while working on Melrose Place she also guest starred in such shows as Grapevine, Partners and Spin City. After Melrose Place , Courtney played the role of the young lawyer Georgia Thomas in Ally McBeal , another FOX network show. Ally McBeal, became an massive international success, and the cast picked up an award from the Screen Actors Guild for Outstanding Performance by an Ensemble in a Comedy Series in 1999. Thorne-Smith stayed with the series until 2000, citing that she wanted to leave the show because of pressure to be so thin and that she wished to spend more time with her new husband Andrew Conrad. Conrad was a genetic scientist and the couple married in June of 2000, however they were divorced a few months after.

1999 also saw Thorne-Smith sign a modeling contract to be the spokeswomen for the 'Skin Stays Fresh' product line for Almay cosmetics.In 2001, Thorne-Smith returned to the TV screen, as Cheryl in the ABC sitcom According to Jim, starring alongside Jim Belushi.

In 2007, Courtney Thorne-Smith wrote a comic novel about the less glamorous side of the L.A. lifestyle called Outside In, published by Broadway Books.