The purpose of this study was to examine the development of self-concept in adolescence according to gender. Using data harvested from the 1st-6th years taken from the Korea Education Longitudinal Study, undertaken by the Korea Educational Development Institute, the sample consisted of 6,908 adolescents who had participated in the Korea Education Longitudinal Study. Multi-level analysis using a growth model was conducted in order to analyze the development of self-concept in adolescence according to gender. The results of this study revealed that the development of self-concept in adolescence changed and underwent linear change in particular during the middle school years. Additionally, there were differences in the growth rates of the self-concept according to gender. First, there were differences in the growth rates in terms of social self-concept according to gender. Second, there were no apparent differences in the growth rates of the family self-concept according to gender. Third, there were no differences in the growth rates in terms of physical self-concept according to gender. Fourth, there were differences in the growth rates of academic self-concept according to gender. The implications and limitations of this study were also discussed.