The objective of the present study was the structural model of borderline personality symptoms based on childhood trauma with the mediation of ego strength in adolescents. The research is applicative and the research method was correlational through structural equations modeling. The statistical population of this research included male and female students of the second secondary level in Tehran in the academic year of 2023-2024. Among the statistical population, 290 people were selected by available sampling method. The research tools included Borderline Personality Disorder Questionnaire (BPQ), Childhood Trauma Questionnaire (CTQ) and ego strength Questionnaire (ETQ). The results showed that the structural model of the research fits the collected data. Also, the results showed that childhood trauma has a direct and significant effect on borderline personality symptoms in adolescents (p=0.001). In addition, the ego strength also have a direct and significant effect on borderline personality symptoms in adolescents (p=0.001). Finally, ego strength positively and meaningfully mediate the relationship between childhood trauma and borderline personality symptoms in adolescents (p=0.001). According to the results of the present study, it can be said that childhood injuries do not act in isolation, but interact with factors such as the ego strength to intensify the symptoms of borderline personality disorder. Understanding these mediating factors provides a more comprehensive picture of how trauma affects psychological outcomes. This integrated perspective is important for the development of targeted interventions aimed at reducing the adverse effects of childhood trauma on adolescent mental health.