Kinnell studied at Princeton University, graduating in 1948. He later obtained a Master's degree from the University of Rochester.
As a young man, Kinnell served in the US Navy and traveled extensively in Europe and the Middle East. His first volume of poetry, What a Kingdom It Was, was published in 1960.
Kinnell became very involved in the U.S. civil rights movement upon his return, joining CORE (Congress of Racial Equality) as a field worker and participating in a number of marches and other civil actions.
Kinnell was awarded the Pulitzer Prize and a National Book Award for Selected Poems (1980), a MacArthur Fellowship, a Rockefeller Grant, the 1974 Shelley Prize of the Poetry Society of America, and the 1975 Medal of Merit from National Institute of Arts and Letters. He served as a Chancellor of the Academy of American Poets from 2001 to 2007.