JoBeth was born in Houston, Texas and attended Brown University. After graduating from college, she joined the Trinity Repertory Company in Providence, Rhode Island and was involved in local theatre. In 1976 - 1977, JoBeth played the role of temptress and news photographer, Brandy Shelloe on the television daytime drama, Guiding Light. In 1979, JoBeth had her film acting debut in Kramer vs. Kramer (1979).

JoBeth is most recognized with her role in Poltergeist (1982) and she reprised her character in the sequel, Poltergeist II: The Other Side (1986). She has starred in a number of TV movies including It Came From the Sky in 1999 with Yasmine Bleeth and small films and has had supporting roles in larger budget films. Williams most recent role is that of a housewife in the Fox Network series 24.

In 1994, JoBeth directed On Hope (1994) which earned her an Academy Award nomination for Best Short Film, Live Action. She is married to TV director John Pasquin and has adopted two children.