The aim of the present study is to investigate how conscientiousness and social capital simultaneously affect auditors’ tendency for whistleblowing in Iranian audit firms. This is an applied and descriptive-correlational research. The statistical sample includes 200 auditors working in the audit organization and private audit firms in 2025, who were selected using the convenience sampling method. The measurement of the research variables was carried out using standard questionnaires, and finally, structural equations were used to analyze the collected data. The results of the research showed that conscientiousness has a positive and significant effect on both social capital as well as on auditors’ tendency for whistleblowing to senior managers of audit firms. The results of this study also confirm the positive and significant effect of social capital on whistleblowing. Furthermore, the mediation analysis indicated that social capital plays a partial and positive mediating role between conscientiousness and whistleblowing. According to the results obtained from this study, conscientious individuals show a more active response when faced with organizational violations due to a higher level of commitment and sense of responsibility in performing assigned tasks. On the other hand, conscientiousness, by strengthening social capital, helps to form a supportive and trusting environment, and in such environments, behaviors such as whistleblowing are associated with greater social acceptance and their likelihood of occurrence increases. Therefore, professional development approaches in the field of auditing should go beyond technical knowledge and regulations. In addition to specialized training, it is necessary to design programs to identify, cultivate, and strengthen positive personality traits such as conscientiousness. Also, creating infrastructures for the development of social capital can provide the basis for increasing transparency and strengthening supervisory mechanisms.