A better understanding of the earning downside risk (default risk) can increase the power of analysis and decision making by investors, stockholders and other users. Better corporate governance is expected to promote good firm performance and reduce default risk because of anticipated reduction in agency cost. The risk management and the corporate governance become critical and important due to the financial turmoil and scandals in recent decades. Using a panel data multiple regression, by 114 firms for the period 2014 to 2018 (570 firm-year) from Tehran Stock Exchange (TSE), this paper explores whether or not a corporate governance mechanism, are associated with its earning downside risk. Our results show that good corporate governance proxies as institutional ownership and non-executive managers reduces downside risk. Likely because their decision-making is more transparent than that of firms without these characteristics. We suggest board and ownership structure can be taken into account for the evaluation of earning downside risk.