The aim of this study is the effect of the product market competition on Investment efficiency in the Tehran Stock Exchange. For this purpose Four hypotheses are developed and data on the 118 companies in Tehran Stock Exchange for the period between the years 2008 to 2015 were analyzed. This regression model using Pooled Data, reviews and tests. The results showed that the measures considered in this study included the Herfindahl index and Hirschman, Lerner index, the index entry barriers to the industry and Tobin's Q index has a negative impact on investment efficiency. In addition, the indicators expressed as an inverse measure for the competition can be claimed, competition in the product market Regarding the effect of which has to create transparency in information and decision-making, Causing a significant positive impact on the Investment efficiency in companies listed on the Tehran Stock Exchange.