The collection consists primarily of correspondence (over 400 boxes) of Kahn during the last twenty-five years of his life when he was prominent as an international banker (with Kuhn, Loeb & Co.), a philanthropist, and a leader in the cultural life of both New York City and the nation. Much of the collection is related to Kahn's business interests in the financial community and in the arts, such as the Metropolitan Opera House where he was chairman of the board. The correspondence reflects not only his generosity as a philanthropist but also the active interest he took in the many groups he supported by serving on administrative and policy-making boards. The scope of Kahn's influence can be seen in the many letters, telegrams, and statements of sympathy from all over the world expressed at his death. As a patron of the arts and an international banking figure, he was often called upon to speak, and the collection contains many pamphlet copies of such public addresses and published opinions, as well as 25 bound volumes of correspondence and clippings regarding them. There is also material assembled by John Kobler while preparing his biography Otto the Magnificent: The Life of Otto Kahn (1988), with the manuscript of his text.

Included among Kahn's correspondents are the world leaders Theodore Roosevelt, Franklin Delano Roosevelt, Woodrow Wilson, and Winston Churchill; and the well-known composers and performers Cleofonte Campanini, Enrico Caruso, George Gershwin, Alma Gluck, Lee Shubert, Jacob J. Shubert, and Arturo Toscanini.