The collection consists of manuscripts and typescripts of various types of works by Symons, including Amoris Victima, Cesare Borgia, Confessions, Figures of Several Centuries, Jezebel Mort and Other Poems, Lorenzaccio, Nero, Parisian Nights, Toy Cart, and Tristan and Iseult; over 30 notebooks; watercolors and paintings; correspondence; tear sheets of contributions by Symons to periodicals (many corrected in manuscript by Symons or prepared as actual copy for book publication); photographs of Symons, members of his family, and friends; clippings of reviews of Symons' books; and articles and clippings concerning art, literature, and people of interest to him, such as Cagliostro, Casanova, Giorgone, Thomas Hardy, Frank Harris, John Addington Symonds, Paul Verlaine, François Vidocq, and Villiers de l'Isle-Adam. Also included are unpublished plays and poems, translations of French and Italian poetry, ballet programs, and miscellaneous correspondence, including three letters from Stephane Mallarme, and eleven letters from John Sampson, the English student of gypsies. There are also 23 watercolors by Welsh artist Gwen John.

A few letters to Symons are also included in this collection; however, the bulk of his correspondence appears to have been dispersed before his death.