<p>Several studies have established the association between social comparison and aggression. However, the underlying mechanisms of the linkage between social comparison and adolescents’ aggression have received limited attention. This study examined social comparison conditions (upward social comparison, downward social comparison, and non-comparison condition) differences in aggression and self-control, and whether differences in aggression were mediated by self-control. A sample of 173 mainland Chinese adolescents (<i>M</i>_age = 13.23 years, <i>SD</i> = 0.83, ranging from 12 to 15) was randomly allocated to the upward social comparison group (<i>n</i> = 59), downward social comparison group (<i>n</i> = 54), or the non-comparison group (<i>n</i> = 60). The results showed that adolescents in the upward social comparison group exhibited the most aggression and the lowest level of self-control, while no significant differences were observed between the downward social comparison and non-comparison groups concerning aggression and self-control. Furthermore, the multicategorical mediation analysis demonstrated that self-control partially mediated the association between the upward social comparison group and aggression relative to the non-comparison group. That is, adolescents in the upward social comparison group displayed lower levels of self-control, which in turn correlated with increased aggression when compared to the non-comparison group. Our findings identified the internal mechanisms of adolescent aggression and provided preliminary evidence for future interventions to decrease adolescents’ aggression within the social context.</p>