Objective: The purpose of this study was to examine the effect of adolescents’ callousness on reactive and proactive aggression through moral disengagement. Methods: The participants were 315 freshmen and sophomore high school student in Korea. The data were analyzed with Structural Equation Modeling(SEM). Results: First, adolescents’ callousness did not show a significant influence on reactive aggression directly or indirectly through moral disengagement. Second, adolescents’ callousness had a significant influence on proactive aggression directly and indirectly through moral disengagement. That is, adolescents' high level of callousness not only predicts a higher level of proactive aggression directly, but also influences moral disengagement which may result in a high level of proactive aggression. In addition, the gender difference in this model was confirmed. Conclusion/Implications: The results of this study indicated that adolescents’ callousness could have different influences on aggression through moral disengagement by the types of aggression and gender. The results suggest that it is necessary to approach the emotional and cognitive process of adolescent aggression differently, depending on the type of aggression and gender.