The paper examines the history of Belarusian émigrés in interwar Czechoslovakia. It is built on the premise that the anti-Soviet Belarusian national programme among the Czechoslovak exiles derived from the democratic ethics of the Paris Peace Conference as well as the idea of the new Czechoslovak state. Based on archival documents, the paper argues that due to international developments and a lack of material resources the mutually beneficial coexistence ended in the mid-1930s. Focusing on the activities of the key Belarusian representative of the Protectorate Böhmen und Mähren, Jan Jermačenko, the paper traces the decay of Czech-Belarusian relations after December 1938. It concludes that the anti-Soviet nature of the new Belarusian program was politically anchored in Germany, while the Czechs preferred Stalin’s antifascism to Hitler’s anticommunism. This split caused a fatal lack of Czech or Slovak willingness to protect Belarusians against Soviet despotism after the Second World War.