This study examined the opposing hypotheses that either low or exaggerated but disputed self-esteem is related to aggression in 652 12-year-old schoolchildren. Children provided peer nominations of social acceptance and of physical aggression, self-ratings of global self-worth and of social satisfaction. Teachers rated aggressive behavior and internalizing problems. Exaggerated but disputed self-esteem was conceptualized as discrepancies between self and peer evaluations of social satisfaction and of social acceptance, respectively, in combination with peer rejection. The main results showed that both low levels of global self-worth and exaggerated but disputed self-esteem were related to aggression. The findings indicated that, depending on how self-esteem is conceptualized, aggressive children may appear to have both a low and a high self-esteem. Regarding gender differences, exaggerated self-esteem was more strongly related to aggression in boys than in girls.