Large‐scale hydroelectric dams have—throughout their history—had adverse impacts on local population groups, natural resources, and entire eco‐systems furthering resistance and protest against them. In this paper, we aim to investigate the impact of social mobilization against large‐scale dams by considering political opportunity structures, actor constellations, and frames. We comparatively analyze three case studies in varying political systems, that is, Gibe III in Ethiopia, Belo Monte in Brazil, and Barro Blanco in Panama. Our investigation is based on field research in these countries comprising data collection of governmental reports, newspaper articles, materials published by civil society organizations, and semi‐structured interviews. The analysis reveals that the impact of mobilization against dams is certainly limited in contexts with authoritarian governments. In democratic contexts, the impact depends on the degree of external involvement, as well as the ability of movements to avoid fracture, especially in view of temporal dimensions of large infrastructure projects.