Jurist and historian; since 1999 provenance researcher in the Museen der Stadt Wien; from 2008 to 2020 provenance researcher in the joint provenance research in Leopold Museum by the Federal Ministry for Arts, Culture, the Civil Service and Sport and Leopold Museum Privatstiftung; member of the Arbeitskreis für Provenienzforschung e.V.; from 1999 to 2003 research assistant in the Historian Commission of the Republic of Austria; several projects and publications on political parties, German nationalism, Nazi art looting and restitution law; in April 2008 award of the Karl von Vogelsang-Staatspreis für Geschichte der Gesellschaftswissenschaften for a monograph "Hitlers Vätergeneration: Die Ursprünge des Nationalsozialismus in der k. u. k. Monarchie".
Kajetan Mühlmann studied from 1913 to 1917 at the k. k. Staatslehrerbildungsanstalt in Salzburg-Stadt together with lifelong friends and future National Socialists Karl Heinrich Waggerl and Karl Springenschmid.