The purpose of this research is to study the impact of earning forecast by management on risk and firm value in Tehran stock exchange during the period from 2007 to 2012. Using systematic sapling method, 101 were selected. The needed data was gathered through the selected firms’ financial statement. In order to test the hypotheses, correlation test and linear regression test were used. An earnings forecast is independent variable which has three characteristics namely accurate, frequency and reliability. Firm value and risk is dependent variable. Control variables include size, financial leverage and intangible assets to total assets ratio, growth, and return on investment. According to the research findings there is a positive and meaningful relationship between earnings forecast and there is a negative and meaningful relationship between earnings forecast and firm risk. The research findings show there is no meaningful relationship between earnings forecast and market risk.