In social psychology it has been argued that the importance of justice cannot be overstated. In the present paper, we ask whether this indeed is the case and, more precisely, examine when fairness is an important determinant of human reactions and when it is less significant. To this end we explore what drives people's reactions to perceived fairness and argue that although social justice research has reported effects of fairness perceptions on people's affective feelings, a close examination of the literature shows that these reactions appear less frequently and less strong than one would expect. It is proposed here that this has to do with the neglect in the social psychology of justice of an important determinant of affective reactions: individuals' propensity to react strongly or mildly toward affect-related events. As hypothesized, findings of two empirical studies show that especially people high in affect intensity show strong affective reactions following the experience of outcome fairness (Study 1) and procedural fairness (Study 2). When affect intensity is low, however, weak or no fairness effects were found, suggesting that then fairness may not be an important issue. In the discussion it is thus argued that incorporating affect intensity into the justice literature may further insights into the psychology of reactions toward fairness.