Dolores Hicks was the only child of a Catholic actor Bert Hicks, and his wife, who, despite the religious implications, separated and ultimately divorced. Hart was also the niece of singer Mario Lanza. It was actually her grandfather, a movie theater projectionist to whom she turned for comfort in light of her parents' marital problems, whose enthusiasm for films influenced her decision to pursue an acting career. At the age of nine she had a bit part in the film Forever Amber, which was finally released in 1947 following a long battle between the movie's producers and the Catholic censors of the day.

Using the stage name of 'Dolores Hart', in 1956 she was signed to play a secondary role as the love interest to Elvis Presley in the 1957 release Loving You. Much in demand, she made two more films before playing with Presley again in 1958's King Creole. She has denied ever having had an 'intimate' relationship with Presley offscreen. Hart then debuted on Broadway, winning a 1959 Theatre World Award as well as a Tony Award nomination for Best Featured Actress for her role in The Pleasure of His Company.

In 1960, Hart starred in Where the Boys Are, a teenage comedy about college students on spring break which developed a near cult-like following. She went on to star in four more films, her last opposite Hugh O'Brian in 1963's Come Fly with Me. At this point she had made up her mind to leave the film industry, and after breaking off her engagement to a Los Angeles businessman Don Robinson, the twenty-five-year old actress became a Roman Catholic nun at the Benedictine Abbey of Regina Laudis in Bethlehem, Connecticut, ultimately becoming the Prioress of the Convent. She chants in Latin eight times a day.

In 2006, she visited Hollywood again after 43 years in monastery to raise awareness for peripheral idiopathic neuropathy disorder, a neurological disorder that afflicts many Americans, including herself.

Today, the Reverend Mother Dolores Hart is Prioress of the Abbey, but has in recent years become the only nun to be an Oscar-voting member of the Academy of Motion Picture Arts and Sciences.