Background: Perceived organizational justice and colleagues’ social support are important factors influencing teachers’ organizational commitment. However, the mediating role of colleagues’ support in this relationship is underexplored, particularly in public schools.

Objective: This study aimed to investigate the relationship between perceived organizational justice and organizational commitment, with the mediating role of colleagues’ social support, among public school teachers in Mahshahr.

Methods: A descriptive-survey method was used. The population included 2,500 public school teachers in Mahshahr, and 335 were selected through stratified random sampling. Data were collected using validated and reliable questionnaires: Niehoff and Moorman’s (1993) Perceived Organizational Justice, Allen and Meyer’s (1990) Organizational Commitment, and Kaplan and Wheeler’s (2008) Colleagues’ Social Support. Structural equation modeling was used for data analysis.

Results: Perceived organizational justice had a significant positive effect on organizational commitment (0.734) and colleagues’ social support (0.682). In turn, colleagues’ social support significantly influenced organizational commitment (0.295), confirming its mediating role.

Conclusion: Strengthening organizational justice and fostering supportive peer relationships can enhance teachers’ commitment and performance in public schools. These findings offer practical implications for educational leadership and policy.