Far-right domestic terrorism is a major threat to US national security. Despite this reality, conservative policymakers have downplayed the threat of right-wing violence while arguing that far-left violence (from groups like Antifa) is a more pressing concern. Drawing on attribution theory and research on politically motivated reasoning, we suggest that politics constrain the American public’s understanding of terrorism by shaping casual attributions for it. Using data from an experiment within a national survey (n = 700), we examine how political views moderate attributions made for the actions of far-right, far-left, and Islamist terrorism. We find that causal attributions for terrorism depend on the type of terrorist considered, with external attributions (motivated by injustice or oppression) endorsed most strongly for Islamist terrorists and internal attributions (motivated by hate or evil) endorsed most strongly for far-right terrorists. Furthermore, political views moderate this effect such that people believe terrorism committed by politically aligned groups is motivated less by the internal characteristics of the terrorists and more by external factors. Taken together, these findings may help to explain partisan differences in moral outrage over politically motivated terrorism.