This article analyzes how economic migration was addressed in the technical institutions of the League of Nations and in the International Labor Organization (ILO), during the initial period of institutional genesis after the First World War. New archival material is used to integrate the fragmented scholarship on migration cooperation and establish dialogue with broader research on the development of international economic governance in the 1920s. This transversal analysis highlights commonalities and interactions that cut across institutional boundaries. Within the League system, different economic institutions carved out limited areas of cooperation in migration policy, while collectively reaffirming national sovereignty over borders and population.