This study assessed the relationships between reactive and proactive aggression and justification beliefs, impulsivity and antisocial behavior, examined characteristically in the context of children but less often studied in adolescents. For this reason the current study assessed a sample of 320 adolescents of both sexes in order to examine the relationships between reactive and proactive aggression and antisocial behavior, impulsivity and normative believes. Results showed that proactive aggression was significantly related to antisocial behavior and normative believes, in both sexes, whereas impulsivity showed the highest correlation to reactive aggression. Using structural equation modeling, a direct relationship was found between aggression and antisocial behavior partially mediated by normative beliefs. According to these results, the authors conclude by stressing the importance of considering impulsivity and normative beliefs as key factors for understanding the development of aggression in adolescents.