One of the important issues that has been considered by researchers in recent years in the wake of widespread financial scandals at the level of large companies and has been raised as one of the most important issues for investors, is the issue of corporate governance. It separates the economic unit from its ownership and ultimately protects the rights of investors and stakeholders. The role of corporate governance in management decisions, including the managers of listed companies, is important. Corporate governance leads to a good opportunity for managers to improve the quality of internal audit in addition to improving the profitability process in companies. Therefore, the purpose of this study is to investigate the effect of corporate governance on the quality of internal audit and decision making of managers. Statistical population In the present study, 83 companies listed on the Tehran Stock Exchange for the period from 1393 to 1398 were selected as the sample size. The results of data analysis showed that corporate governance has a significant and positive effect on the quality of internal audit and managers' decisions.