: This paper show the effect of corporate governance and audit quality on the credit cost of listed companies in Tehran stock exchange. Financing system in Iran is bank oriented, but banks and other financial institutions have little share in corporate governance structure of companies. So they may attend about the controlling quality and quantity procedures exerted and also the quality of financial reporting. Therefore it is expected an adverse relation between cost of debt and quality of corporate governance which result from efficient monitoring of the board of directors and institutional block shareholders and audit quality. Our result on the basis of the 119 companies of Tehran stock exchange between years 1382 to 1387, and using pool data regression method with Eviews3 program, shows that existence of the institutional block shareholders in shareholders composition of the company and efficient monitoring of them has a meaningful decreasing effect on the cost of debt of the statistical companies, but the audit quality has no effect.