Hans Ankwicz von Kleehoven, an art historian with a doctorate, joined the civil service as a concept trainee in the archive and library of the Imperial-Royal Ministry of Education in 1907. In 1912 he married the publicist and art critic Alexandra Sauer-Csáky von Nordendorf. In February 1915, Ankwicz von Kleehoven enlisted as a war volunteer and was assigned to the heavy field artillery regiment no. 2 and later to the infantry regiment “Hoch- und Deutschmeister” no. 4. After his deployment on the Isonzo Front in November 1915, he was transferred to the Russian theatre of war in 1916. In 1917, he worked for the regimental museum of the “Deutschmeister” in Vienna before he had to return to the front in Italy in August 1918. At the end of November 1918, Ankwicz-Kleehoven was discharged as a first lieutenant. By June 1915, he had already transferred to the Austrian Museum of Art and Industry, where he was in charge of the library and works on paper collection  from 1925. He was also active as a publicist, art educator and art consultant, and was a member and co-founder of various associations such as the Austrian Exlibris Society. Ankwicz-Kleehoven was also active as an art collector.

After the annexation of Austria to the German Reich in 1938, the Chief State Librarian, who – as was recorded in his Gauakt – sympathized with the NSDAP, initially remained in office. Ankwicz-Kleehoven played a decisive role in the takeover of the Wiener Werkstätte archive by the State Museum of Decorative Arts in March and April 1939. At the end of April 1939, he was forced to retire on the basis of the decree on the reorganization of the Austrian civil service of 31 May 1938, as he was considered a “first-degree Mischling” according to the Nuremberg racial laws. While he had to give up his many years as art editor of the Wiener Zeitung, Ankwicz-Kleehoven was able to publish in the Nazi magazine Kunst dem Volke. His attempt to join the Reichsschrifttumskammer (Reich Literature Chamber) failed in 1941, and from the fall of 1942 he worked as an archivist at the Künstlerhaus.

After the end of Nazi rule, the art historian was reinstated to the civil service with effect from 27 April 1945 on the basis of Section 4, Paragraph 1 of the Law for the Restoration of the Austrian Civil Service and promoted to State Librarian General. Transferred to the Academy of Fine Arts on 11 October 1945, he was promoted to director of the library, which also included the Kupferstichkabinett. Ankwicz-Kleehoven resumed his work as art editor of the Wiener Zeitung. He also worked on his own encyclopedia of artists, which he was unable to complete. He retired on 31 December 1949, after which he devoted more time to his publishing activities and his private collection, which included hand drawings, paintings and (commercial) graphics by Egon Schiele, Gustav Klimt, Koloman Moser, Otto Ledecke, Richard Teschner, Franz Wacik, Remigius Geyling, Felix Albrecht Harta, Edvard Munch and Dagobert Peche, as well as autographs, picture postcards, bookplates and books. In 1953, part of this collection was exhibited in the Österreichischen Staatsdruckerei (Austrian State Printing House) under the title Glück des Sammelns (The Happiness of Collecting). Hans Ankwicz-Kleehoven died in 1962 and bequeathed a number of items from his collection to the library of the Academy of Fine Arts Vienna in his will, the majority of which were auctioned by Christian Nebehay in 1964.