The purpose of this study was to examine the impact of different types of organizational culture in auditing firms on auditors’ professional competence, with an emphasis on the mediating role of behavioral entropy. Considering the importance of audit quality in enhancing public trust and reducing information risk, identifying the factors influencing auditors’ professional competence is essential. This applied research employed a descriptive-correlational design. The statistical population of this study included auditors working in audit firms that are members of the Iranian Society of Certified Public Accountants with a professional rank of supervisor and above. To determine the sample size, according to Haier et al. (2018), at least 5 samples were used for each item, and the minimum sample size required was estimated to be 455 people. 600 questionnaires were distributed using the convenience sampling method, and ultimately 489 questionnaires were collected. Structural equation modeling (SEM) was used to test the hypotheses. The findings revealed that developmental, hierarchical, and group cultures had a positive and significant effect on auditors’ professional competence, whereas rational culture did not have a significant effect. Furthermore, the mediating role of behavioral entropy was only significant in the group culture and was not confirmed for other cultural types. The type of organizational culture—particularly a group-oriented culture—can effectively enhance auditors’ professional competence by reducing behavioral disorder and increasing mental coherence. It suggests that audit firm managers provide a suitable platform for enhancing the professional and ethical capabilities of auditors by strengthening supportive and collaborative cultures.