Background and Purpose: The psychological wellbeing of adolescents has always been a focal point of research topic. Ignoring this issue could have irreversibly adverse effects on individuals and societies. The present study investigated the mediating role of sexual intimacy in relationships between the attitude and sexual health and self-differentiation of mothers with the psychological wellbeing of adolescents living in Ahvaz City, Iran.
Materials and Methods: Conducted during the academic year 2021–2022, the descriptive-correlational recruited study students from Ahvaz senior high schools and their mothers. Using the stratified cluster sampling, 300 students and their mothers participated in this study as the study sample. The research instruments included the psychological wellbeing scale, the attitude scale toward sexual health, the differentiation of self-inventory, and the marital intimacy questionnaire. The Pearson correlation coefficient was used to assess the correlation between the study variables. Bootstrap analysis gauged the significance of mediating relationships. Structural equation modeling (SEM) was employed to evaluate the proposed model using SPSS software, version 27 and AMOS software, version 25. 
Results: The results showed that all direct paths to the psychological wellbeing of adolescents were significant, except for the self-differentiation of mothers (P<0.001). Moreover, the indirect paths from mothers’ attitude toward the sexual health to the psychological wellbeing of adolescents and the correlation between mothers’ self-differentiation and the adolescents’ psychological wellbeing were significant when mediated by the sexual intimacy of mothers (P<0.001). 
Conclusion: The proposed method demonstrated a good fit. Improving the sexual intimacy of mothers is expected to boost the psychological wellbeing of adolescents. It is recommended to hold workshops to promote effective communication skills and self-differentiation for couples to enhance the sexual intimacy of mothers, thus boosting the psychological wellbeing of adolescents.