Alicia made her film debut in David Lynch's Dune and, by the age of fourteen, received her high school diploma and moved to Los Angeles, California, to pursue acting full time. Once she was in Los Angeles, Lynch cast her in his Emmy Award-winning cult classic television series Twin Peaks as Gersten Hayward, a part written specifically for her. Following this, Lynch utilized Alicia's talents once again in his HBO trilogy Hotel Room, in which she portrayed a young woman with multiple personality disorder. Alicia appeared in Mr. Holland's Opus opposite Richard Dreyfuss as well as in Four Rooms (Miramax/Buena Vista) with Tim Roth, Madonna Ciccone, and Lili Taylor, which was directed by Quentin Tarantino, Allison Anders, Robert Rodriguez, and Alexandre Rockwell. In 1994, Witt appeared in the critically acclaimed Fun, which debuted at the Sundance Film Festival. The film, directed by Rafal Zielinski, depicts two disturbed young girls whose quest for fun leads them to murder. Witt received the Special Jury Recognition Award at Sundance and a nomination for an Independent Spirit Award. Other credits include Mike Figgis's Liebestraum starring Kevin Anderson, Bodies, Rest & Motion starring Tim Roth and Bridget Fonda, and Bongwater opposite Luke Wilson.

She combined her acting talents with her skills as a classically trained pianist in the romantic comedy Playing Mona Lisa. For this role, Alicia won a Best Actress Award at the U.S. Comedy Arts Festival. Alicia has made guest appearances on the phenomenally successful HBO series The Sopranos and the Emmy Award-winning Ally McBeal. In 1998, Alicia starred in Columbia Tristar's hit movie Urban Legend. Witt's home for four years was CBS, where she starred as Zoey, Cybill Shepherd's quirky daughter with a dark side, on the sitcom Cybill (Carsey-Werner).

More recently, Witt was in The Upside of Anger opposite Kevin Costner and Joan Allen and in Curse of the Ring, which was shot in South Africa. She was last seen starring in the Warner Bros. romantic comedy Two Weeks Notice opposite Hugh Grant and Sandra Bullock. She was also seen in the John Waters film Cecil B. DeMented starring Stephen Dorff and Melanie Griffith. Alicia also made a cameo in the independent film American Girl.
Used to play the piano at the Regent Beverly Wilshire Hotel. Appeared on That's Incredible! at the age of four because of her amazing reading skills. She also performed the balcony scene of Romeo and Juliet with the host. Parents are Robert and Diane. Brother is Ian. Was home schooled and received high school diploma at age fourteen. Is a classically trained pianist. In June 2004, she modeled what is claimed to be the most expensive hat ever made, the US$2,700,000 Chapeau d'Amour by celebrity couture hat designer Louis Mariette, at Christie's in London. Grew up down the street from screenwriter Caitlin McCarthy in Worcester, Massachusetts. McCarthy wrote the adapted historical drama "Vera," which will star Lucie Vondrácková, Alicia Witt's co-star in Last Holiday. Her mother is Diane Witt, who was in the Guinness Book of World Records from 1988 to 1996 for having the world's longest hair. Her brother Ian Rob Witt appeared with her in the film Liebestraum (1991)_ .