Freed by the February Revolution, Piatnitsky relocated to Moscow, where he became a member of the Bolshevik Party's Moscow Committee. Following the Bolshevik Revolution of November 1917, Piatnitsky became a government functionary. From 1919 to 1920 he served as head of the Railroad Workers' Trade Union. Piatnitsky was chosen as head of the Moscow Committee in 1920 and elected an alternate member of the governing Central Committee of the Russian Communist Party (bolsheviks) at the party's 9th Congress that same spring.