After attending Saint Mary's College (Indiana), across the street from the University of Notre Dame in South Bend, Indiana, where she studied theology, Hicks began a career in acting. She first rose to prominence as Dr. Faith Coleridge on the soap opera Ryan's Hope, a role she played from 1976 to 1978. In 1979, she was one of the leads in the television version of The Bad News Bears and in 1982 she took the lead role in the comedy/detective series Tucker's Witch opposite Tim Matheson. Supporting roles in movies followed, with appearances in Star Trek IV: The Voyage Home as Dr. Gillian Taylor, and Peggy Sue Got Married as Carol Heath (both 1986), but it was the role of the mother in the movie Child's Play (1988) that first established her as a name in Hollywood. The next year, she starred opposite Tony Danza in She's Out of Control.

In the first half of the 1990s, Hicks found acting work in the form of made-for-TV movies, but it wasn't until 1996 that she got another popular role. She was cast as preacher's wife Annie Camden on the drama 7th Heaven (opposite fellow Star Trek alum Stephen Collins), which is arguably her most famous role to date. 7th Heaven has just completed filming it's tenth and, originally, final season, making it the longest-running family drama on television. In a surprise move at the upfront for the new CW Television Network and their '06/'07 season, it was announced that because of the stellar ratings of the supposed series finale the show will return for at least 13 episodes (edging out Everwood for the chance to return) next season.

Resides with her family in Bel-Air, California.