Mary Ellen Moylan was born on August 24, 1925, in Cincinnati, Ohio, to an Irish builder father and schoolteacher mother.

[3][5] In 1942, at age 17, Moylan made her New York stage debut in a one-off Balanchine ballet Pas de Trois for Piano and Two Dancers, alongside Nicholas Magallanes for a Russian War Relief performance.

[3] The same year, the 17-year-old Moylan was cast in Strauss' operetta Rosalinda, choreographed by Balanchine, with her and José Limón as the principal dancers.

"[3] On her performance in Ballet Imperial, New York Times critic John Martin commented, "She is definitely a talented dancer who is worth watching.

She had also danced Balanchine's works with the company, including Concerto Barocco, Serenade, Le Bourgeois Gentilhomme and Danses concertantes.

[1][5] In 1946, Moylan left Ballet Russe to perform Alan Jay Lerner and Frederick Loewe's musical The Day Before Spring on Broadway, with choreography by Antony Tudor.

[2][5] Reviewing this performance, critic Edwin Denby concluded that among Ballet Society's roster, "Mary Ellen Moylan is its bold young ballerina.

[3][5] Having studied singing and acting, Moylan returned to Broadway in 1947, in Straus' The Chocolate Soldier, also choreographed by Balanchine, with her and Moncion as the lead dancers.

[5] Her repertory with the company included lead roles in The Sleeping Beauty, Swan Lake, Giselle, Don Quixote pas de deux, Balanchine's Apollo, Theme and Variations, Tudor's Jardin aux Lilas and Petit's Les Demoiselles de la Nui.

Then, she moved to Pleasant Valley, New York, and worked at Bennett College as a ballet teacher, purchasing agent and campus shop manager.