While it is generally agreed that income inequality affects an individual's well-being, researchers disagree on whether people living in areas of high income disparity report more or less happiness than those in more equal environments, thereby indicating the need to study how and why income inequality matters to the individual's well-being. Findings on group-specific reaction patterns to income inequality further fuel this need. Alesina et al. (2004) argue that a preference for inequality and the perception of the possibility of social mobility account for the indistinct relationship between income inequality and subjective well-being. Combining this hypothesis with previous research on social cognition and drawing on social justice theory, this paper aims to demonstrate the mediating nature of perceptions of income inequality. It argues that the perceived legitimacy of distributive outcomes and procedures contributes to how income inequalities affect individuals and their sense of well-being. The empirical analysis is based on data from the International Social Justice Project, developed from face-to-face interviews with a representative sample of the German population. Using structural equation modeling, the paper finds structural biases in the perception of income inequality. The paper concludes that subjective well-being is a product of the individual's perception and legitimating processes. The results indicate that social cognition is a useful tool for studies of income inequality and subjective well-being.