This work deals with the organization of aid committees on behalf of Soviet political prisoners in the 1920s. After a brief overview of the main groups operating on the Soviet territory, it focuses on the relief activities of Russian émigrés in Paris and Berlin. There, various political Red Crosses attempted to arouse European public opinion on the horrors of the Red Terror. They also asked European and American workers to show socialist solidarity to their imprisoned comrades. At the hand of two specific organizations of Berlin émigrés, the Aid Society for Political Prisoners and Exiles in Russia and the United Committee on behalf of Imprisoned Revolutionaries in Russia, this works explores the principles of solidarity towards political prisoners in the 1920s, as well as some issues related to Russian political emigration in Berlin.