Narcissists have a relatively higher proclivity for displaying antisocial rather than prosocial behaviors, suggesting a comparatively higher tendency for unfavorably impacting societies. However, maintenance of social order also depends on appropriate responses to others' social behavior. Once we focus on narcissists as observers rather than actors, their impact on social functioning becomes less clear-cut. Theoretical arguments suggest that narcissists could be either hypo-responsive or hyper-responsive to others' social behavior. Across four studies, we examined narcissists' responsiveness to variations in others' antisocial and prosocial behaviors. Results showed that narcissists differentiated less between others' antisociality/prosociality, as reflected in their subsequent moral character evaluations (Studies 1-4) and reward and punishment (Studies 3 and 4). These results suggest that narcissists are hypo-responsive to others' social behaviors. Implications and directions for future research are discussed.