The purpose of this study is to examine the effect of organizational justice on organizational commitment and deviant behavior among organizational employees. In terms of purpose, the study is applied, and in terms of method, it is descriptive-survey research. The statistical population consisted of 346 employees of Bank Mellat in Tehran Province, who were selected through stratified random sampling. A questionnaire was used as the data collection instrument. Data were analyzed using SmartPLS software.The findings indicate that interpersonal justice has a significant negative relationship with unlawful behavior, such that higher perceptions of respect and fair interpersonal treatment lead to a reduction in violations. In addition, procedural justice is positively and significantly related to interpersonal justice, and both distributive and procedural justice have a direct and positive relationship with affective commitment. On the other hand, although unlawful behavior showed a direct and significant relationship with negative behavior, no significant relationship was found between unlawful behavior and affective or normative commitment. In contrast, negative behavior had a significant negative relationship with both affective and normative commitment. These findings suggest that while organizational commitment can act as a deterrent to everyday negative behaviors, unlawful behaviors may be influenced by factors other than commitment, such as structural monitoring mechanisms.In conclusion, enhancing employees’ perceptions of justice in its distributive, procedural, and interpersonal dimensions is an effective strategy for increasing affective commitment and reducing deviant behaviors in service organizations such as banks. Managers should therefore focus on improving process transparency and the quality of human interactions in order to foster constructive behaviors.