Bullying is an act of verbal, nonverbal, and physical violence. The cause is not trusting each other so that they bully each other even though the problem is trivial. In adolescence, individuals begin to have more abstract and reasonable thoughts, as well as the ability to draw conclusions from events. However, at this age emotions are still relatively unstable so that at this stage many are controlled by the emotions that exist in themselves. Teenagers who are victims of bullying tend to reflect on the distress they have experienced. They have a tendency to remember bad things that have happened in their lives and find it difficult to forget them, which is commonly called rumination. Previous research with child and adolescent subjects found that adolescents who experience victimization more often tend to experience rumination that causes anger and sadness. Moral Disengagement is considered a cognitive process that individuals use to justify behavior that they know is wrong. The purpose of this study was to determine the role of Moral Disengagement in moderating the relationship between anger rumination and bullying behavior in adolescents. This research uses a quantitative approach with a research design using ex-post facto which is carried out after a phenomenon occurs. Based on the results of the study, it was found that anger rumination has a significant role in the emergence of bullying behavior in bullying victims (Sig. 0.000 < 0.005). The results of this study support previous research on rumination and anger rumination in the development of bullying behavior. Interaction between variables X and Y is not significant, P = 0.886 (>0.05) which means that anger rumination does not affect bullying. Likewise, the interaction between variables M and Y is also not significant, P = 0.7945 (>0.05) which means that moral disagreement variables do not affect bullying behavior. The results of the research show that anger rumination plays a non-significant role in the emergence of bullying behavior in bullying victims (Sig. 0.8836 < 0.005). The results of this study do not prove the effect of anger rumination on the emergence of bullying behavior. This result is not in accordance with previous research on rumination and anger rumination affecting the emergence of bullying behavior.
 Keywords: anger rumination, bullying, moral disengagement