Background: Evidence indicates that being a victim of bullying or peer aggression has negative short- and long-term consequences. In this study, we investigated the mediating and moderating role of two types of attributional mechanisms (hostile and self-blaming attributions) on children's maladjustment (externalizing and internalizing problems). Methods: In total, 478 children participated in this longitudinal study from grade 5 to grade 7. Children, parents, and teachers repeatedly completed questionnaires. Peer victimization was assessed through peer reports (T1). Attributions were assessed through self-reports using hypothetical scenarios (T2). Parents and teachers reported on children's maladjustment (T1 and T3). Results: Peer victimization predicted increases in externalizing and internalizing problems. Hostile attributions partially mediated the impact of victimization on increases in externalizing problems. Self-blame was not associated with peer victimization. However, for children with higher levels of self-blaming attributions, peer victimization was linked more strongly with increases in internalizing problems. Conclusions: Results imply that hostile attributions may operate as a potential mechanism through which negative experiences with peers lead to increases in children's aggressive and delinquent behavior, whereas self-blame exacerbates victimization's effects on internalizing problems. (Contains 2 tables and 2 figures.)