The problem of agency appears as a result of the difference in goals between the agent and the owner. Concentrated ownership is a situation where a few large shareholders own a significant portion of the company's stock. By having a large share, the largest shareholder can monitor the company more accurately and easily and limit the management from doing ineffective work and also reduce information transparency and information asymmetry in the company. Therefore, the purpose of this research is to study the effect of ownership concentration on the relationship between tax evasion and information asymmetry. The statistical research population of companies admitted to the Tehran Stock Exchange and the studied sample includes 140 admitted companies during the years 2017 to 2018. The research method is descriptive and in terms of the relationship between the variables, it is causal-correlation, and in terms of the objective, it is applied, and in terms of the event, it is post-event. The regression method and panel data as well as the fixed effects model were used to process and test the hypotheses. The results obtained from the hypothesis analysis showed that ownership concentration has a negative and significant effect on the relationship between tax evasion and information asymmetry.