The Subject of this study is narcissism, self-esteem, and aggression in adolescents. The aim of the current study was to investigate the relationship between narcissism, self-esteem and dimensions of aggression and compare sex differences in these variables in adolescents.258 adolescents (124 boys and 134 girls) 14-18 years old, were selected by using multistage cluster random sampling method and were assessed by Narcissistic personality inventory (NPI-16) self-esteem and Aggression questionnaires. Data were analyzed using Pearson's correlation coefficient, multiple regression analysis and T test. The results showed positive significant relations between narcissism, self-esteem and aggression and negative relations between self-esteem and aggression. Multiple regression analysis showed that low self-esteem is most responsible in predicting aggression in adolescents. The findings showed no sex differences in features of narcissism and self-esteem among adolescents and sex differences in the dimensions of aggression was observed only in physical aggression. The results of this study can be beneficial for a better understanding of theoretical and clinical relationship between narcissism, self-esteem, and aggression in adolescents.