Following the February Revolution in 1917, Klestov became a member of the Bolsheviks (RSDLP(B)) and was a member of the Executive Committee of the Moscow Soviet, running their press section. He attended the Seventh (April) Conference and Sixth Congress of the RSDLP(B), at which he was criticised by Stalin. He participated in the October Revolution in Moscow and played a role in the Military Revolutionary Committee, Khamovniki district. He worked for the Moscow Soviet until 1929. He edited the journal "Tvorchestvo" (1919–22), the literary collections "Nedra" (1922–24), and ran the publishing house Nedra (1924–29). He was appointed trade representative for the USSR in Lithuania from 1929 to 1931 and then in Greece from 1932 to 1936.