Why are some countries more successful at advancing the clean energy transition than others? Existing studies focus largely on industrialized democracies and frame domestic and international explanations against each other. Instead, we develop a unifying framework around the idea of credibility to explain clean energy transition outcomes in developed and developing countries and shed light on the prospects for future reform efforts. We elucidate the credibility challenges reformers confront and point to new directions for the comparative and international study of energy transi- tions necessary to respond to the climate crisis.