Neuwirth was born in Princeton, New Jersey, the daughter of Sydney Anne, an artist, and Lee Paul Neuwirth, a mathematician. Neuwirth is Jewish and attended the Chapin School of Princeton, but graduated from Princeton High School (a public school) in 1976. She began to study dance at the age of five, and chose it as her field of concentration when she attended Juilliard in New York City in 1976 and 1977. During this period, she performed with the Princeton Ballet Company in Peter and the Wolf, The Nutcracker, and Coppelia and appeared in community theater musicals.