The purpose of this study was to examine the effects of proactive and reactive aggression on adolescents’ internalized/externalized problem and the mediating effect of executive function. Participants were 283 adolescents in Seoul and Gyeonggi-do province and they were asked to complete the self-report questionnaire about proactive and reactive aggression, internalized/externalized problem and executive function. The results were as follows. First, There were significantly positively correlation between proactive/reactive aggression and internalized/externalized problem and were significantly negatively correlation between proactive/reactive aggression and executive function. And there were significantly negatively correlation between internalized/externalized problem and executive function. Second, the mediating effects of executive function on relation between proactive/reactive aggression and internalized/externalized problem were partially significant. The mediating effect of executive function on relation between reactive aggression and internalized/externalized problem is significant, but the mediating effect of executive function on relation between proactive aggression and only externalized problem is significant. Based on the results, the implications and limitations of this study were discussed.