Existing results about the impact of regime type on states’ environmental performance are inconclusive. This could stem from failure to allow for economic inequality—a largely overlooked factor. More equal democratic societies, we contend, are likely to make greater progress in dealing with environmental problems. However, inequality undermines those processes and characteristics of democratic polities that are supposed to further environmental protection. In contrast, inequality is unlikely to be of much importance in authoritarian states. Using data on carbon emission performance for the post-1970 period, we find strong and robust evidence that inequality moderates the influence of democracy. Our research adds to the debate about regime type and environmental politics.