Robert Penn Warren has the unique distinction of serving as both the third Consultant in Poetry to the Library of Congress (1944-1945) and the first Poet Laureate Consultant in Poetry to the Library of Congress (1986-1987).

Warren accepted the position of Consultant in Poetry on May 2, 1944, and began his term that July. His primary responsibility as Consultant was to serve as editor of the Quarterly Journal of the Library of Congress, a position he took over from the previous Consultant in Poetry, Allen Tate External. He did not necessarily enjoy the work, describing it in an October 16, 1944, letter to Robert Heilman External as a "quarterly crisis" in which "once every three months I get into a swivet and am torn from my pleasant poetical musings and occupations into the stern realities of editing."

In addition to editing volume 2 (November 1944-June 1945) of the Journal, at the request of Librarian of Congress Warren contributed an article in the volume's first issue on "The War and the National Muniments External," about the relocation of the Declaration of Independence, the Articles of Confederation, the Constitution, and other seminal documents to Fort Knox during World War II. Warren and Tate were the only two Consultants to serve as editors of the Quarterly Journal; editorial responsibility for the Journal was turned over to Library employee John Lester Nolan in October 1945.

Another significant accomplishment during Warren's tenure as Consultant was to continue the poetry recording project initiated by Allen Tate. During his consultantship Warren brought in thirteen poets, as well as several novelists, to record their work in the Library's Recording Lab. These recordings form part of the Library's Archive of Recorded Poetry and Literature.

As part of his work developing the Library's literary collections, Warren compiled a bibliography, Poets of the Golden Age, documenting American poetry published between 1860-1910, designed as a tool to identify and fill in gaps in the Library's collections. Warren, who worked in Room L in the Attic of the Jefferson Building, which would later become the Poetry Office, was assisted in this and other duties by Sheila Corley, one of his former graduate students at Louisiana State University.

Warren also continued writing fiction and literary criticism during his Consultantship. Most notably, he worked on his novel All the King's Men ("I grind along on a new novel," he wrote in the aforementioned letter to Heilman) and a study of Samuel Taylor Coleridge's The Rime of the Ancient Mariner.

On February 26, 1986, more than forty years after Warren served as Consultant in Poetry, Librarian of Congress Daniel Boorstin appointed Robert Penn Warren the first Poet Laureate Consultant in Poetry to the Library of Congress. While the position's new title increased its visibility, the essential requirements of the position did not change. For instance, while the UK's official poet laureate was expected to write poems celebrating or commemorating events of national significance, the Poet Laureate Consultant in Poetry would be under no such obligation. Warren pointedly noted in a telephone interview with the New York Times External that he would not have accepted the appointment had he "been required to compose an ode on the death of someone's kitten," and that he had no interest in being a "hired applauder."

Warren's appointment as poet laureate was the third most popular Library-related story in the press for fiscal year 1986, according to the Library's annual report for that year External. It generated "more than seventy-five press calls," and although Warren remained at his home in Fairfield, Connecticut, for the announcement (and most of the laureateship), he "was willing to talk to the many reporters who had called the Information Office for interviews, to pose for pictures, and to admit television crews to his home."

Warren began his term as poet laureate with an October 6 reading of his poem entitled "Sirocco," followed by author James Olney reading and commenting on Warren's work.

Warren's activities as poet laureate were limited by ongoing health issues. On March 29, 1987, in Warren's absence, the Library hosted a program titled "A Legacy of American Poetry," consisting of a series of readings celebrating Warren and the laureateship. This program formed part of a larger three-day celebration External honoring the fiftieth anniversary of the Consultantship in Poetry.

On May 4, 1987, a lecture by Warren on Herman Melville's poetry was delivered by John C. Broderick, the Assistant Librarian for Research Services. Broderick stepped in to read the lecture when health issues prevented Warren from traveling to the Library. The subject of Warren's lecture was originally meant to be on the subject of contemporary literary criticism ("What Sense or Nonsense does the Phrase 'New Criticism' Have? External") but he had a change of heart. As reported by the Chicago Tribune in a June 1, 1987, article External, Warren noted the reason for the change in the new lecture read by Broderick:

Some weeks before sitting down to write this I had finished what was supposed to be this lecture. But I didn`t like it. The subject was Literary Criticism in Our Time—a discussion of that absurd term `New Criticism.` I looked over what I had done and I was bored stiff. I began to wonder whether I would be alone in that boredom tonight. So I turned to a subject which has fascinated me for now many years—in fact, almost all my adult life. In fact, as I worked at the first version of this lecture, I was reading Melville`s poems

On June 10, 1987, approximately one week after the end of Warren's term as poet laureate, Warren was named a recipient of the National Medal of Arts. The Library's John Broderick received the award on Warren's behalf External from President Reagan at a June 18 White House luncheon.