The aim of the present study was to investigate the mediating role of anger rumination in the relationship between trait anger and aggression and the moderating role of moral disengagement. This research is in the form of correlational path analysis and more precisely modeling the moderating mediator. The statistical population of this research was all the twelfth grade students of the second period of high school in the academic year of 2021-2022 in Ahvaz city, from which 200 students were selected using a multi-stage random sampling method. The instruments used in this research included the Aggression Questionnaire (Buss & Perry, 1992); Trait-State Anger Expression Inventory– 2 (Spielberger, 1999); Anger Rumination Scale (Sukhodolsky, Golub & Cromwell, 2001); and Civic Moral Disengagement Scale (Caprara, Fida, Vecchione, Tramontano & Barbaranelli, 2009). The evaluation of the proposed model was done through the Software SPSS 22 and PROCESS method, model No. 15. Results showed that trait anger had a positive and significant relationship with aggression and anger rumination was the mediator of this relationship. Moral disengagement moderated the conditional direct relationship between anger rumination and aggression and the relationship between trait anger and aggression at two levels (out of three levels). Regarding the conditional indirect results between trait anger and aggression through anger rumination, moral disengagement moderated this relationship only at two levels (at the mean and one standard deviation above the mean). Overall, by incorporating moral disengagement as a moderator into the model, the current study detected effects that would have been neglected without the moderation analysis.
