This study was conducted to investigate the mediating role of mentalization in the relationship between traumatic childhood experiences and aggression in adolescents. This descriptive-correlation study was based on structural equation modeling. The statistical population of this research was the female students of second secondary level in Rasht city in the second half of 2022. 250 people participated in a multi-stage cluster method from three public high schools for girls. For data collection, the Childhood Trauma Questionnaire (CTQ; Bernstein et al., 2003), Aggression Questionnaire (AQ; Buss and Perry, 1992), and Reflective Performance Questionnaire (RFQ; Ha et al., 2013) were used. The results showed that the proposed model is a good fit. The results showed that the direct effect of traumatic childhood experiences with aggression, uncertainty, and certainty mentalization was significant, and the direct effect of uncertainty and certainty mentalization on aggression was significant (P<0.05). Other results showed that certainty and uncertainty mentalization play a mediating role between traumatic childhood experiences and aggression (P<0.05). In general, it can be concluded that traumatic childhood experiences directly and indirectly with the mediation of mentalization can affect the level of aggression in adolescence.