Between the mid‐1930s and the beginning of the Second World War, a group of German seamen based in Antwerp combined with Amsterdam‐based Edo Fimmen, secretary of the International Transport Workers' Federation, to wage a campaign against the Nazi government among the sailors of the German merchant fleet. They organized cells of supporters on German ships, encouraged informal resistance, circulated propaganda and planned sabotage. The Antwerp Group was a breakaway from the Comintern‐aligned International of Seafarers and Harbour Workers (ISH). The Antwerp men were reacting against the ineffectiveness of the response of the German communist leadership to Hitler's takeover of power, and against the growing subordination of the ISH to Soviet interests. By highlighting the role of anti‐Stalinist militants in the anti‐fascism of the 1930s, the article contributes to the recent scholarship on anti‐fascism – a scholarship that has tended to emphasize the transnationalism and ideological diversity of anti‐fascism, rather than seeing it in national terms, or as a monolithic entity controlled by Moscow.