She married her first husband, Martin Sacker, in 1944, and divorced him in 1951. Subsequently, Cabot was romantically linked with King Hussein of Jordan for several years. She bore her only child, a son, in 1961. In 1968, she married her second husband Michael Roman with whom she raised her son, Timothy Scott Roman, before again divorcing in 1983.

She made her film debut by chance when Kiss of Death (1947) was filmed in New York, and she played a bit part. She expanded her acting work into television and was seen by a Hollywood talent scout who took her to Hollywood to work for Columbia Pictures. This brief period was not successful, and she moved to Universal Studios where she was signed to an exclusive contract. After a series of roles for which Cabot was mainly cast in B-movie westerns, she became dissatisfied and asked to be released from her contract. She returned to New York, where she resumed her stage career with a role in A Stone for Danny Fisher. She was invited to return to Hollywood and appeared in a few more films, including The Wasp Woman (1959), her final film role.

In the weeks immediately prior to her death, Cabot's mental health deteriorated significantly. On December 10, 1986, Cabot's 25-year-old son, Timothy Scott Roman, beat her to death in her home in Encino, California, with a weightlifting bar. He was charged with second-degree murder.

At the close of the trial, prosecutors changed the charge to voluntary manslaughter, as no evidence had been presented at trial to support premeditation (which was required for a murder conviction). Superior Court Judge Darlene E. Schempp deliberated 10 minutes, and then convicted Roman of involuntary manslaughter. Roman, who had already spent two-and-a-half years in jail, was sentenced to three years' probation on November 28, 1989.