Efficient market hypothesis predicts that capital markets are beset with cer-tain biases which result from wrong estimation, and negatively influence shareholders’ expectations for higher returns, which in turn affects invest-ment efficiency, financial constraints and corporate performance efficacy in competitive markets, and eventually mitigates firm value. The present study aims at examining the impact of CEOs’ perceptual biases on investment efficiency and financing constraints of the firms listed on the Tehran Stock Exchange over the period 2013-2017. Earnings forecast error and CEOs’ overconfidence biases serve as the measure of CEO’s perceptual biases, the model developed by Biddle et al (2009) is employed to proxy for investment efficiency, and KZ model is also adopted to calculate financing constraints. The results reveal that both earnings forecast error and overconfidence biases negatively affect investment efficiency, while they positively influence cor-porate financing constraints. Manuscript profile