Though the concept of social justice is widely used in the social sciences, we know little about the amount of income inequality that is perceived as just and why perceptions vary across social contexts. In this paper, we argue the ways people define the causes of poverty are related to how they perceive and justify existing income inequality. We examine internal and external attributions of poverty using survey data from the 2006 International Social Justice Project (ISJP). We compare two culturally and structurally distinct regions—East and West Germany. The results support our hypothesis that the amount of income inequality people perceive as just is related to how they explain the causes of poverty, that is, internal and/or external attributions. Poverty attributions are crucial mediators and explain contextual differences in the perceived justice of income inequality between East and West Germany.