The bulk of the materials are published and unpublished writings of Hilaire Belloc including manuscripts, typescripts, proofs, and galleys; reprints of various articles, essays, reviews, poetry, plays, prose, notes; and about eighty of Belloc's books. Among the other publications in this collection are a series of reviews of Belloc's books and articles; commentary on Belloc's politics; parliamentary materials saved by Belloc; and printed materials including book notices, lecture notices, syllabi, speeches, news clippings, leaflets, advertisements, and weekly journals.

The collection also contains visual materials, including artwork and photographs, such as illustrations for Belloc's New Cautionary Tales drawn by Nicolas Bentley and photographic portraits of Hilaire Belloc, family members, friends, and associates. Other photographic materials include images of Belloc's King's Land Estate, photo albums, and sailing and ship photos. Also included in the visual materials are a photograph of Sir James Dunn's painted portrait of Hilaire Belloc, Maurice Baring, and G. K. Chesterton, entitledThe Conversation, and over 1,000 printed maps.

Of particular note is an unpublished autobiography dictated by Belloc around 1936 and some sound recordings of Belloc's songs, including a phonographic disc entitled The Authentic Voice of Hilaire Belloc Singing with Ian Wallace, pressed around 1970. The remainder of the materials in this collection include financial records, typescript diaries, memoranda and agenda, and approximately 30 manuscript diaries variously attributable to Hilaire Belloc, Elodie Hogan Belloc, and Elizabeth Hogan.

Additional materials include scrapbooks, materials found in scrapbooks, and an array of printed materials such as postcards, an honors certificate, and two honorary degrees bestowed upon Hilaire Belloc.