Felix Mandl had graduated at the Medical School of the University of Vienna in 1919 with the academic degree 'Dr. med'. After that he worked as operating trainee until 1932 and alter as assistant professor at the Second surgical university hospital. In 1928 he became lecturer ('Dozent') for Chirurgie at the Medical School of the University of Vienna, from 1933 on he was head of the surgical Department of the S. Canning Childs-hospital.
He was persecuted in times of Nazism as a Jew lost his position and was thrown out of the university on April 22nd, 1938. He also lost his position in the hospital.
Felix Mandl emigrated via Switzerland and France to Jerusalem/Palestine in 1938/39, where he became head of the Second surgical department of the Hadassah university hospital and was appointed professor in 1940.
He returned to Austria in 1947, became head of the surgical Department of the Kaiser Franz Josef-hospital in Vienna and again lecturer for surgery at the University of Vienna. In 1948 he was appointed extraordinary professor (ao. Prof.). Mandl officiated as communal councilor of the Sozialistische Partei Österreichs (SPÖ, Socialist Party of Austria) in Vienna from 1954 to 1957.