Kelley began his career with the San Carlo Opera in New York in 1948 and made his New York City Opera debut as the Magician Magadoff in Gian Carlo Menotti's The Consul in 1952. He made his Metropolitan Opera debut in 1957 as Mime in Wagner's Ring cycle and the following year performed the title role in the City Opera world premiere of Robert Kurka's The Good Soldier Scheweik.

Other NYCO premieres Kelley sang include the Reverend Samuel Parris in Robert Ward's The Crucible in 1961, Lord Mark in Douglas Moore's The Wings of the Dove in 1962, and Ely Pratt in Carlisle Floyd's The Passion of Jonathan Wade in 1962.

At the Met his roles included Shuisky in Boris Godunov, Herod in Salome, Don Basilio in Le nozze di Figaro and Alcindoro in La Bohme. In 1967, the Met used Kelley's English-language translation of Humperdinck's H‹nsel und Gretel in a new production directed by Nathaniel Merrill; the libretto has been frequently used at the Met since then.

Kelley was born on August 27, 1911, in Eddington, Maine. He studied at the New England Conservatory, Pasadena College and Eastman Conservatory. He did military service from 1940 to 1945 and appeared on the radio show "Fort Bragg Salutes America."

He died of Alzheimer's disease, according to The New York Times.