Given that the efficiency and quality of internal control systems implemented by management are key factors in a business entity's survival, this study examined the impact of internal control structures on organizational ethical behaviors, considering the mediating role of internal control effectiveness and the moderating role of organizational culture. This research was applied in nature and employed a descriptive-correlational method, utilizing a questionnaire for data collection. The statistical population consisted of 802 specialists responsible for designing and implementing internal controls (financial deputies and senior financial managers of companies listed on the Tehran Stock Exchange); a sample of 260 individuals was selected using Cochran's formula. Smart-PLS 3 software was used to analyze the research hypotheses. Test results indicated that internal control structures, internal control effectiveness, and organizational culture all influenced organizational ethical behavior. The findings revealed that internal control effectiveness mediated the impact of internal control structures on organizational ethical behaviors. Furthermore, the results demonstrated that organizational culture moderated the effect of internal control structures on organizational ethical behaviors; thus, employee relationships, their role in making sound and efficient decisions, inter-departmental communication, and work environments that facilitate resource sharing and the exchange of ideas all influence internal control structures and organizational ethical behaviors. Organizations should simultaneously focus on improving the quality of their internal control structures and strengthening their organizational culture to ensure maximum internal control effectiveness.