Messing was born in the Brooklyn borough of New York City. She is the daughter of Sandra (née Simons), who has worked as a professional singer, banker, travel agent and real estate agent, and Brian Messing, a sales executive for a costume jewelry packaging manufacturer. The Messing family is Jewish, and descends from Russia and Poland. When Messing was three, she moved with her parents and her older brother, Brett, to East Greenwich, a small town outside Providence, Rhode Island.