Although exploring arguably darker themes, Kinnell has been regarded as being in line with Walt Whitman in his rejection of the idea of seeking personal fulfillment by escaping into the imaginary world.

Upon returning to the US, he joined CORE (Congress of Racial Equality) and worked on voter registration and workplace integration in Hammond, Louisiana.

[7] Alongside other personal themes and anxieties, Kinnell drew upon both his involvement with the civil rights movement and his experiences protesting against the Vietnam War in his 1971 poem cycle The Book of Nightmares.

[9] Kinnell was the Erich Maria Remarque Professor of Creative Writing at New York University and a Chancellor of the American Academy of Poets.

[11] For instance, "The Fundamental Project of Technology" deals with all three of those elements, creating an eerie, chant-like and surreal exploration of the horrors atomic weapons inflict on humanity and nature.

Scholars have also identified, on the contrary, themes of optimism and beauty in his use of language, especially in the large role animals and children have in his later work, evident in poems such as "Daybreak" and "After Making Love We Hear Footsteps".

[12] In addition to his works of poetry and his translations, Kinnell published one novel (Black Light, 1966) and one children's book (How the Alligator Missed Breakfast, 1982).

Kinnell married Inés Delgado de Torres, a Spanish translator, in 1965 — naming their two children, Fergus and Maud, after figures in Yeats.