This publication deals with the communist activities in Ciechanów County from 1918 to 1939. The goal of the article is to analyze the initiatives of the members of the Communist Workers’ Party of Poland and then, since 1925, the Communist Party of Poland, along with its agendas and sympathetic organizations. The source material does not allow for a complete reconstruction of the twenty-year existence of the party in the county. Nevertheless, it allows capturing the essence of its functioning. The basic forms of activity for the communists in Ciechanów County consisted of distributing appeals, hanging banners, and organizing strike actions.This publication deals with the communist activities in Ciechanów County from 1918 to 1939. The goal of the article is to analyze the initiatives of the members of the Communist Workers’ Party of Poland and then, since 1925, the Communist Party of Poland, along with its agendas and sympathetic organizations. The source material does not allow for a complete reconstruction of the twenty-year existence of the party in the county. Nevertheless, it allows capturing the essence of its functioning. The basic forms of activity for the communists in Ciechanów County consisted of distributing appeals, hanging banners, and organizing strike actions.