Background: Peer influence on adolescent delinquency is well established, but little is known about moderators of peer influence. In this study, we examined adolescents' (targets) and their peers' psychopathic personality traits as moderators of peer influence on delinquency in peer networks. We used three separate dimensions of the psychopathic personality: grandiose-manipulative traits, callous-unemotional traits, and impulsive-irresponsible traits. Methods: We used a peer network approach with five waves of longitudinal data from 847 adolescents in one community. Peer nominations were not limited to the school context, thus allowing us to capture all potentially important peers. In addition, peers reported on their own delinquency, thus allowing us to avoid problems of false consensus or projection that arise when individuals report on their peers' delinquency. We used simulation investigation for empirical network analyses (SIENA), which is the only program currently available that can be used to study peer influence effects in peer networks of multiple relationships while controlling for selection effects. Results: Targets' and peers' callous-unemotional and grandiose-manipulative traits uniquely moderated peer influence on delinquency. Relative to those with low levels, targets who were high on these traits were less influenced by peers' delinquency, and peers who were high on these traits were more influential on targets' delinquency. Selection effects were found for impulsive-irresponsible traits, but these traits did not moderate peer influence on delinquency. Conclusions: As the first study to look at moderating effects of psychopathic traits on peer influence, this study advances knowledge about peer influence on delinquency and about psychopathic traits in adolescents. In addition, the study contributes to the literature by looking at unique effects of the three dimensions of psychopathy and taking a peer network approach, in which network effects, self-selection, and other selection effects are controlled when examining influence and moderators of influence.