After the Second World War, Mildenstein continued to live in West Germany, where he joined the Free Democratic Party and was elected to its Press Committee. In 1956, he went to Egypt to work for a radio station, and after the capture of Adolf Eichmann in 1960 he claimed immunity as an intelligence agent of the US Central Intelligence Agency, a claim which was neither confirmed nor denied. Nothing was heard of him after 1964, when he published a book on cocktails.