Winzer joined the Socialist Unity Party, the East German communist party, in 1945, and he became a member of its central committee in 1946. He was named the deputy editor of the party's official paper Neues Deutschland in 1949. Winzer was Secretary of State from 1949 to 1956 and First Deputy Minister of Foreign Affairs from 1956 to 1965. He served as Minister of Foreign Affairs from 1965 to 1975. He was removed from his post due to ill health and died at age 72 on 3 March 1975.