According to the ‘low self-esteem hypothesis’, low self-esteem plays a causal role in aggression among adolescents, whereas ‘threatened egotism theory’ postulates that aggression is related to a highly favorable view of the self. The primary purpose of the present study was to investigate the effect of self-esteem on aggression among adolescents. Based on the theoretical background, a research model was constructed. The present study analyzed the 5th and 6th wave data from Korea Children and Youth Panel Study (KCYPS). The results showed that self-esteem had a significant negative effect on aggression among high school students. Finally, research implications which contribute to enhancing self-esteem as well as decreasing aggression were also discussed.