Born as Dolores Hicks on 20 October 1938 in Chicago, Illinois, to teenage parents, Bert and Harriet, who were both aspiring actors, Dolores Hart was primarily raised by her grandparents, as her father left his family for Hollywood to pursue her career as an actor, when she was only 3-year-old. Her grandfather was a projectionist at a cinema hall, and young Hart often accompanied him to the projector booth and watched the larger-than-life figures on the screen, which influenced her future decision to pursue an acting career. She converted to Roman Catholicism when she was 10, and by the age of 11, she was living in Beverly Hills with her mother, attending the all-girls Catholic Corvallis High School in Studio City, Los Angeles. After high school, she was admitted to Marymount College, where she was spotted by an agent of Hal Wallis, in a production of Joan of Lorraine, and consequently, signed as Dolores Hart at the age of 19, to play the role of Susan Jessup, the love interest of Deke Rivers, played by Elvis Presley in Loving You (1957), in which she had even locked lips with Elvis Presley, his first on-screen kiss, and turned her a major starlet.

With the release of her first films, Dolores became an overnight success story, and stepped with ease into playing the role of the innocent Angie with Anthony Quinn in Wild Is the Wind (1957), and also appeared as Justy Sargeant with Montgomery Clift in Lonelyhearts (1958), before starring with Elvis Presley again in King Creole (1958), a musical teen drama film, playing the role of Nellie. The next year, she appeared in two TV serials, and then played the role of Ellie Walters in the western drama film The Plunderers (1960), and also appeared as Merritt Andrews, a college girl falling for a suave rich college boy Ryder Smith, played by George Hamilton, in the romantic comedy-drama Where the Boys Are (1960), which was a box office hit.

Connie Francis, Dolores Hart, Yvette Mimieux, and Paula Prentiss, on the set of Where the Boys Are

By that time, Dolores was dubbed as the new Grace Kelly, and starred in the comedy heist movie Sail a Crooked Ship (1961), in which she appeared as Elinor Harrison, the kidnapped girlfriend of Gilbert Barrows, played by Robert Wagner. However, the role of Clare in the religious drama film Francis of Assisi (1961) landed in her lap while she was holidaying in Europe. Filmed entirely on location in Italy beginning the week after Dolores turned 22 in October 1960, the film lost money at the box office, but it was memorable for Dolores Hart for another reason. While in Rome, she was invited to tour the Vatican and met Pope John XXIII, and when she introduced herself as Dolores Hart, the actress playing Clara, Pope John XXIII rectified her by saying that she was Clara, which influenced her future life.

The next year, Dolores Hart co-starred with actor Stephen Boyd in the World War II drama Lisa (aka The Inspector 1962), in which she appeared as Lisa Held, a Auschwitz survivor trailed by ex-Nazis. While filming on location in London, Hart was arrested for a night, and got locked out of her apartment after a long day of shooting and was taken for a homeless vagrant. Although she was quickly released, her arrest made the newspapers. During that time, a friendship began off set between Dolores and Stephen Boyd, when they had supper almost every night and discussed religion and their lives. Nevertheless, after that, she portrayed the role of Dona Stuart, a flight attendant in the romantic film Come Fly with Me (1963), also starring Karl Malden. Incidentally, since then, Dolores became close with Karl, and his family, which included his wife and their two daughters.

By that time, Dolores Hart met Los Angeles architect Don Robinson in 1960 during a blind double date, and after dating for several years, they became engaged shortly after the filming of Come Fly with Me. A wedding date was set for February 1963, and Dolores asked Malden's daughters, Mila and Carla, to be her bridesmaids. The couple began actively planning their future, including renovations on a new house. Wedding invitations were printed, and Hollywood movie designer Edith Head started creating a wedding dress as a gift for Dolores. After a few fittings for the dresses, Dolores visited the Malden family to inform them that she was calling off the wedding. A few days later, she returned with all her valuables, including her purses, jewellery, and clothes, and asked Mila and Carla to take whatever they wanted. She told them she was moving away and that it was a matter of her inner voice. Although she still loved Don, she explained that not every love ends in marriage. Her decision hurt him deeply, but he remained a close friend, and despite dating other women, he never married. He visited Dolores every Christmas and Easter and gave thoughtful gifts to both Dolores and the monastery.

Dolores was aware of the hardship in the life of a nun since 1959, when following a gruelling run on Broadway, she was encouraged by one of her friends to visit the monastery for peace and rejuvenation. Although initially hesitant, when ultimately she visited the Abbey of Regina Laudis in Bethlehem in Connecticut for the first time, she found a sense of internal peace and tranquillity, and made it a habit to visit the abbey periodically, sometimes twice a year. However, she made her final decision in 1963, when at the peak of her career, she stunned Hollywood by tossing away the glamorous world of entertainment, and entered the Abbey of Regina Laudis in her entrance ceremony, accompanied at the gates by her friend Maria Cooper and her mother, whom she conveyed her decision only the night before. She was allowed to take two calls that came in shortly after her entry, one of which was from Elvis Presley, who told her he was happy about her decision and praying for her, and the other call was from Stephen Boyd, who was supportive, but was less thrilled with her decision.

Mother Dolores served as the dean of education at the Abbey of Regina Laudis in Connecticut, overseeing spiritual and vocational formation. She also significantly contributed to the arts and community development at the abbey, and founded The Gary – The Olivia Theater, an open-air theatre and arts program for the Bethlehem community, serving as a bridge between the cloistered life and the public. Although she left the film industry, she remained a member of The Academy of Motion Picture Arts and Sciences (AMPAS), and visited Hollywood again in 2006, after 43 years in the abbey, to raise awareness about idiopathic peripheral neuropathy, often shortened to neuropathy, which refers to damage or disease affecting the nerves that afflict her and many Americans. Notably, she attended the 2012 Academy Awards, her first red-carpet Oscar event since 1959, for the screening of a documentary film on her life, titled God Is the Bigger Elvis, nominated for an Academy Award in the year. Her autobiography, The Ear of the Heart: An Actress' Journey from Hollywood to Holy Vows, co-authored with Richard DeNeut, was released on 7 May 2013.