In 1931, he was sent back to Greece to restore order in the highly factionalised KKE and in the same year, he was elected General Secretary of KKE. In 1935, during the 7th Congress of the Communist International, he was elected to its Executive Committee. In the years until 1936, Zachariadis was a successful leader of the KKE, tripling the number of its members, gaining seats in the Greek Parliament, and even acquiring control of some labor unions.