This paper examines the impact of internal audit (IA) practices on the performance of commercial banks. Six factors were investigated, including the application of international IA standards, the independence and objectivity of the IA, the quality and professionalism of IA members, gender diversity within the IA department, the size and frequency of meetings, and management support for IA. Using questionnaires, data were collected from 34 commercial banks in five Arab countries: Saudi Arabia, Yemen, Sudan, Somalia, and Djibouti. Structural equation modeling (SEM) was performed using SmartPLS 3.3.3. The results demonstrate the significant and direct influence of the examined factors on the performance of commercial banks, except for the professional competence of internal auditors. Additionally, the study reveals that the performance of internal auditors, as a mediating variable, does not significantly affect the relationship between the internal audit system (IAS) and bank performance. This paper makes a significant contribution to the field of auditing as it is the first study to examine IA in Arab countries using multiple factors. The findings of this study can be utilized by regulators, such as the Institute of Internal Auditors (IIA), bank owners and managers, government agencies, and central banks.