The purpose of this study was to investigate the relation between male adolescent friendship jealousy and maladaptive emotion regulation strategies and aggression. The subjects were 204 middle school second graders. The main findings of the study were as follows, 1) There was a significant correlation between friendship jealousy and all emotion types. 2) The type of friendship jealousy was significantly different according to the maladaptive emotion regulation strategies. 3) The type of friendship jealousy was significantly different according to relational aggression. 4) The relational aggression was affected by blaming-others strategies.