Institutional investors play important role on formation of different changes on corporate governance systems. They can significantly influence on companies by monitoring the performance of management and limiting their opportunistic behaviors and manipulating their financial statements. Therefore, the main objective of the present study is to investigate the relationship between institutional investors and earnings management on some listed companies on Tehran Stock Exchange by examining a sample of 700 firm-years data over the period 2006-2010. In this study, the discretionary accruals are used as an indicator for earnings management. The results indicate that there is a positive and significant relationship between institutional investors and earnings management and suggest that increasing the ownership percentage of institutional shareholders increases earnings management. In addition, the results of the control variables have shown that firm size had no impact on earnings management, but financial leverage and return on sales, respectively had negative and positive effect on the earnings management of companies.