This paper explores the effect of national partisanship and Euroscepticism on individualsÕ causal responsibility attribution in European multilevel democracies. It is particularly focused on the average differences in responsibility attribution in federal and non-federal states, as well as in countries belonging to different European Union enlargement waves. Using a pooled dataset of the 2004, 2009, and 2014 show that when poor economic outcomes are at stake, partisans of the national incumbent in federal states are more likely to assign responsibility to regional governments following a blame-attribution logic, while this logic is absent in non-federal states. Likewise, Eurosceptic individuals are more likely to assign responsibility to European authorities when they hold negative views of the economy and they belong to countries that have been European Union members for a longer period. 3 One of the most celebrated virtues of multilevel systems is better democratic governance. Indeed, classical normative theories state that multilevel governance helps to allocate power more efficiently to the most relevant level and enhance the control of governments by bringing them closer to citizens and overcoming informational asymmetries between representatives and represented. However, a more critical view stresses that vertical fragmentation of power makes the latter unable to establish a causal link between incumbentsÕ performance and outcomes, hampering their capacity to assign responsibilities. From this perspective, the peril of multilevel governance lies in that it makes voters less capable of attributing responsibility, weakening the rewardpunishment model and, in turn, electoral accountability.Certainly, individualsÕ capacity to assign responsibility between levels of government lies at the heart of the accountability mechanism of the reward-punishment model (Cutler 2004(Cutler , 2008 DŠubler et al. 2017). In this paper, the goal is to advance research on responsibility attribution by exploring responsibility judgements in multilevel systems. Building upon the political science literature on retrospective accountability and the social psychology literature on cognitive bias, the paper explores the role of party identification and attitudes towards the European Union in individualsÕ responsibility assignments, and tests for variation in this effect between different institutional contexts. In essence, the specific research questions are namely two: do group-serving biases in responsibility operate more intensely in multilevel systems than in countries with a unitary form of government? Do they operate more prominently in contexts where levels of governments are more consolidated?This paper provides new theoretical and empirical insights into the role of cognitive biases in responsibility attribution, with a particular focus in the variation between different institutional contexts. The first hypothesis assumes that multilevel 4 governance activates the use of cognitive bias in responsibility attribution, and th...