Darling was born in Baltimore, Maryland. Inspired by the folk music group The Weavers, in the '50s, he formed The Tunetellers, later called The Tarriers with actor/singer Alan Arkin. Their version of the "Banana Boat Song" reached #4 on the Billboard charts.
Darling left that group to replace Pete Seeger in The Weavers, staying with them from 1958 through 1962. He then formed The Rooftop Singers, who had a number one single with the song "Walk Right In", and his solo album True Religion for Vanguard was influential on younger folkies of the day. Don McLean who became friends with Darling in 1961, looked back on Darling as “a genuine philosopher and perfectionist.” He said, “I appreciated the time he spent with me so long ago. Undivided mental attention to every aspect of music making and performing is a hallmark of Erik’s work, and I believe some of that rubbed off on me.”.
In 1967, Darling and Paul Bennett were co-credited for writing the song "Babe I'm Gonna Leave You," by Quicksilver Messenger Service, which appears to be a medley of Darling's 1958 song "St. John's River" and Joan Baez's "Babe I'm Gonna Leave You".