Introduction: Students’ sense of responsibility has a substantial impact on their academic and professional progress, as well as the future of their society. Therefore, it is necessary to examine and identify factors influencing their sense of responsibility. Aim: The present study aimed to propose a model of responsibility based on identity styles with the mediating role of self-concept. Method: In this correlational study, the path analysis method was applied. The study population consisted of all students of Tehran University of Medical Sciences, Shahid Beheshti University of Medical Sciences, and Science and Research Branch of Islamic Azad University in 2022. A total of 411 students were selected via random cluster sampling. The data collection tools were Kurdlo's Responsibility Questionnaire (2015), Identity Style Inventory (1989), and Rogers’ Self-Concept Scale (1957). Pearson's correlation coefficient test was carried out using AMOS version 24 and SPSS version 25 for statistical analysis. Results: The correlation coefficients indicated significant positive correlations between informative and normative identity styles and the sense of responsibility, with the mediating role of self-concept, while the diffuse/avoidant identity style had a significant negative correlation with the sense of responsibility (P<0.01). Moreover, the coefficients were significant for the indirect effects of informative identity style (β=0.028, t=5.17), normative identity style (β=0.047, t=4.32), and diffuse/avoidant identity style (β=-0.056, t=-3.27) on the students’ sense of responsibility, with the mediating role of self-concept (P<0.05). The direct path coefficients for all three identity styles in predicting responsibility were also significant (P<0.01). Conclusion: The present results showed that self-concept mediated the students’ sense of responsibility based on identity styles. Therefore, authorities should take the necessary measures to improve the students’ sense of responsibility, depending on their identity styles.