Peer aggression and victimization are ubiquitous phenomena in schools which warrant the attention of educators and researchers. The high connection between aggression and victimization behooves researchers to look into how the comorbidity of them develops over time. The present study investigated the associations between aggression and victimization over 3 years in early adolescence and whether these associations are moderated by gender and teacher support. Participants were 567 Grade 7, 8 and 9 students (49.38% girls) from 3 schools in Hong Kong. Over the course of study, they were asked to fill in a set of questionnaires that consisted of items related to peer aggression, victimization, and teacher support at 5 time points. Four models of cross-lagged relations between peer aggression and victimization were tested. The results supported a reciprocal model of peer aggression and victimization for both boys and girls although girls engaged in less peer aggression and victimization than boys. Further analyses also revealed that teacher support acted as a suppressor of the reciprocal relations. The present study sheds lights on intervention strategies that may remediate peer aggression and victimization in schools.