Barrett was born in Shreveport, Louisiana, and she grew up in Oklahoma. Like many youngsters who would go on to find acting success, as a child Nancy put on plays in her backyard, co-starring her sister, Martha. Nancy attended Baylor University in Waco, Texas, for two years. There, she met Ivan Rider, then a drama professor (later a director in New York), who was the greatest influences on her early years on stage.After her second year at Baylor, Nancy and two girlfriends spent a summer in Los Angeles. She starred in a production of "Little Mary Sunshine", and fell in love with Los Angeles. She transferred to UCLA, where she graduated a year later. She then played the lead in L.A., in "The Fantasticks" (with Bill Bixby, later the star of TV classics "My Favorite Martian" and "The Incredible Hulk"). From there, she moved to New York and more stage work. She made her Broadway debut in "Pickwick" along with Davy Jones (who later starred in "The Monkees" on TV).In 1966, Nancy became part of the original cast of Dark Shadows (1966), in the role of Carolyn Stoddard, daughter of Elizabeth Collins Stoddard, the family matriarch played by screen legend Joan Bennett. While on the show (playing seven characters in 405 episodes), Nancy took breaks to appear in plays, including Neil Simon's "The Star-Spangled Girl" and "The Physicists".Nancy was married briefly and divorced in the early 60s. While on Dark Shadows, Nancy was married to co-star David Ford. The couple also divorced. In the early 1970s, she married Dr. Harold Kaplan, a prominent New York psychiatrist. Dr. Kaplan died in January1998. Before his death, Nancy's husband got a chance to see her fulfill a dream. For years she'd considered performing a one-woman show, and in August 1997, she did, in "As If We Never Said Good-bye", at the annual Dark Shadows Festival in New York City. She has since performed similar shows in Las Vegas, Los Angeles, the mid-west, and at the New York cabaret club, ,Don't Tell Mama'.During the holiday season of 1999, Nancy made her ballet debut in a production of "The Nutcracker". She is currently in the planning stages of a music CD which she hopes to have completed in early 2003.