The mumok collection today comprises around 10,000 works by c. 1,600 artists. In 1959, the first purchases were made for the newly founded Museum des 20. Jahrhunderts, which held 90 works when officially opened in 1962.
A key impulse for the museum's exhibition and collecting policy was provided by the Ludwig and Hahn Collections in the 1970s, which were shown from 1979 in a second building, the Palais Liechtenstein. The Hahn Collection was purchased by the Republic of Austria, whereas the loans by Peter and Irene Ludwig were permanently guaranteed for the museum by establishing the Austrian Ludwig Foundation. The Republic of Austria agreed in turn to provide a budget that has enabled the Foundation to expand its collection of key works of international modernist and contemporary art - to this day.
The mumok collection consists of several "blocks" that correspond to the different stages in the museum’s history. The period to after World War Two is covered by holdings in classical modernism that were purchased by the museum's founding director, Werner Hofmann. A further focus is the Ludwig and Hahn Collections, with their emphasis on the avant-gardes of the 1960s and 1970s. In the last 15 years a comprehensive collection of Vienna Actionism has been built up. mumok collects contemporary art with an emphasis on photography, video, and film, as well as painting, sculpture, and installations, works which have mainly been added to the collection over the last two decades.