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 of correspondence, memoirs, and printed materials. The correspondence is made up of letters sent by his mother, Olǵa Kostyleva, from Petrograd in 1916-1919. Kostylev's extensive manuscript memoirs (522 p.) discuss his life from his childhood and university education in St. Petersburg up into World War I. Also included are issues and clippings from "Slovo" and "Rus"́ with articles by Kostylev, and clippings from "Poslednie Novosti" by various newspapers.