King was born in Oyster Bay, Long Island, New York. King is a first-generation American; her mother was English and from Liverpool. She appeared in her first commercial when she was six months old. When she was about five years old, she appeared in the television film Inherit the Wind as Melinda. King is a member of the Joseph Jefferson Theatre Company, and her professional credits include summer stock and Off-Broadway productions. She had a small role in the comedy film Between the Lines (1977) before appearing as a Dancer in both Saturday Night Fever (1977) and Hair (1979).

In 1980, King portrayed Alice Hardy, the heroine, in the horror film Friday the 13th. The following year, she reprised her role as Alice in the sequel Friday the 13th Part 2 and starred in a Downy commercial. After the success of Friday the 13th, King was pursued by a stalker. The stalker drew on some of her paintings, and tried to break the door down in her apartment. Shaken by the experience, she decided to take a break from acting and focus on painting. She subsequently relocated to London, where she enrolled at the Royal Academy of Dramatic Art, studying voice and dance. King subsequently became a voice Actress and provided voice work for films such as What's Eating Gilbert Grape? (1993).

In 2009, she signed on to the science fiction/horror film Psychic Experiment, marking her first onscreen film appearance in 27 years. In 2012, she starred in the Welsh Christmas horror film Silent Night, Bloody Night: The Homecoming, an unofficial sequel to the 1974 American horror film Silent Night, Bloody Night and The Butterfly Room. King is set to portray Jackie Winters, an investigative reporter, in the upcoming horror film William Froste and Theresa in the short film Admonition. Aside from acting, King works as a winemaker and wine company coordinator in Oregon.