As an emerging federal system, the European Union (EU) divides decision-making powers between multiple levels of government. Yet little is known about how EU citizens attribute responsibility to the EU. In particular, do people hold the EU, rather than national governments, responsible for different policy outcomes, some of which are primarily decided at the EU level? This article investigates the extent to which institutional differences and individual biases influence citizens’ attribution of responsibility in the EU. We rely on unique survey data collected in all 27 EU member states to explore how citizens attribute responsibility across five different policy areas. Using a multilevel model of responsibility judgments, our findings show that while citizens’ evaluations correspond to the institutional context, group-serving biases, related to support for the EU, have a more important role in shaping attributions of responsibility in the EU.