Adolescents experience various forms of strain in their lives that may contribute jointly to their engagement in cyber aggression. However, little attention has been given to this idea. To address this gap in the literature, the present longitudinal study examined the moderating influence of peer rejection on the relationship between cyber victimization at Time 1 (T1) and subsequent cyber aggression at Time 2 (T2; 6 months later) among 261 (150 girls) 6th, 7th, and 8th graders. Our findings indicated that both peer rejection and cyber victimization were related to T2 peer-nominated and self-reported cyber aggression, both relational and verbal, after controlling for gender and T1 cyber aggression. Furthermore, T1 cyber victimization was related more strongly to T2 peer-nominated and self-reported cyber aggression at higher levels of T1 peer rejection. These results extend previous findings regarding the relationship between peer rejection and face-to-face aggressive behaviors to the cyber context. In addition, our findings underscore the importance of utilizing multiple methods, such as peer-nomination and self-report, to assess cyber aggression in a school setting.