This article examines the impact of populism on environmental politics, focusing on countries’ outcome-level performance. I develop the argument that populist leadership likely undermines environmental quality. First, populist leaders tend to reject and refrain from implementing “green” policies, as these are usually promoted by “corrupt elites.” Second, populism erodes democratic institutions, thus offsetting a series of mechanisms that are related to better environmental outcomes. Empirically, I combine data from the Global Populism Database covering sixty-six countries and more than two hundred executive leaders with information on environmental performance at the outcome level. The findings suggest that populist leadership is strongly linked to lower environmental performance—also when controlling for a series of alternative influences and distinguishing between left- and right-wing populism. This research greatly adds to our understanding of the determinants of environmental policies, the role of regime type and ideology, and the literature on populism.