How do populist attitudes shape evaluations of democratic legitimacy in a system of multilevel governance? While populism is often associated with dissatisfaction with political institutions, it remains unclear whether this discontent is directed equally toward the European Union and the national level. Bridging theories of EU legitimacy and research on populist attitudes, this article examines three institutional mechanisms of democratic legitimacy: whether political institutions are perceived to listen to citizens, explain their decisions clearly, and respond to citizens’ concerns. These dimensions capture key aspects of input, throughput, and output legitimacy, while allowing for comparison across levels of governance. Using original survey data from Germany and Spain, the analysis shows that populist attitudes are associated with more negative evaluations across all three dimensions, but not uniformly across levels.