Hart was born in Trenton, New Jersey. Her father was a teacher and later became a school principal. She graduated from Horace Greeley High School in Chappaqua, New York, where her father was the school principal.

Early in her career she appeared in several Broadway stage productions, notably in the U.S. production of British playwright Peter Nichols' Passion, for which she received a Tony nomination in 1983. She has been seen in a number of films, including The Verdict, Once Around with Holly Hunter, and The Good Girl with Jennifer Aniston.

Hart has been married to actor Philip Casnoff since 1984, and they have two sons.