The collection includes correspondence, manuscripts, memoirs, diaries, notes, subject files, documents, photographs, and printed materials. Most of the material in the collection concerns Nikolaev's tenure as military attachʹe at the Russian embassy in Washington. Cataloged correspondents include Mikhail T. Florinsky and Geroid T. Robinson. There is a typescript by Vasiliĭ O. Kli︠u︡chevskiĭ, "Kratkoe posobie po russkoĭ istorii." Among the correspondence are cablegrams and official communications to the Russian embassy during World War I and the revolutionary period. Manuscripts, mostly by Nikolaev, concern contemporary and historical military topics. Diaries and memoirs deal with Nikolaev's travels to Europe during World War I and his activities as military attachʹe. Among orders granted to Nikolaev is the "Order of the Sacred Treasure," signed and sealed by the Japanese Emperor Meiji (1911). Printed materials include many articles by Nikolaev.

The papers consist primarily of the Kosatkin-Rostovskiĭ's memoirs. His manuscript memoirs (150 p.) discuss his life up to 1906. Her typescript memoirs (440 p.) discuss her childhood, career as an actress in St. Petersburg, 1917-1918 in Petrograd, and the emigration in France. Also included are his diary for June-July 1940; a few letters written to him; clippings of his newspaper articles (many signed with the pseudonym "Antar"); and a book with his poetry and with essays dedicated to him; "Krestnym putem k voskresenii︠u︡" (Paris, 1948).