He studied art history at the University of Vienna from 1911 to 1914 under Josef Strzygowski and Max Dvořák.
He was awarded a doctorate in the history of stained glass in 1919 and as an art expert for the Vienna Dorotheum.
He published his dissertation as a book and wrote catalog texts for exhibitions and for auction After the annexation of Austria by Hitler's Third Reich on 12 March 1938, Jews were removed from the art trade and their businesses transferred to non-Jews.
He worked for Mühlmann's Nazi looting organisation, "Dienststelle Mühlmann," and was appointed by the Reich Commissar for the Netherlands, Arthur Seyß-Inquart, as the "collective administrator" for the art objects confiscated from "enemy property" which generally meant from Jews.
[10][11][12] The Office of Strategic Services Art Looting Investigation Unit placed Kieslinger on their Red Flag List of Names, describing him as a "With Plietzsch, chief professional member of the Dienststelle Muehlmann; chiefly active in Holland, also occasionally in France and Italy.