Thyssen was tried for being a supporter of the Nazi Party. He did not deny that he had been a Nazi supporter until 1938, and he accepted responsibility for his companies' mistreatment of Jewish employees in the 1930s, although he denied involvement in the employment of slave labour during the war. On 2 October 1948, a denazification tribunal declared Thyssen a lesser offender and sentenced him to a fine of 15% of his assets. Thyssen agreed to pay 500,000 Deutschmarks () as compensation to those who suffered as a result of his actions, and was acquitted of other charges. In January 1950, he and his wife emigrated to Buenos Aires, where he died the following year. Thyssen was buried in the family mausoleum in Mülheim.