This paper examines the effect of institutional investor’s investment horizons on corporate social responsibility (CSR). Using data on U.S. firms’ CSR ratings from Kinder, Lydenberg and Domini (KLD) over the 1995-2012 period, we find that the presence of long-term institutional investors mitigates managerial short-termism. It appears that long-term oriented institutions have more incentives to monitor, and that this will push managers toward engaging in more CSR activities. Specifically, our results show that investment horizon of institutions is positively related to CSR, and also that long-term (short-term) institutional ownership is positively (negatively) related to CSR. Overall, our findings suggest that firms with good CSR activities are preferred by investors with long-term horizons.