The purpose of this study is to analyze the relationship between operational risk and accounting conservatism. The criterion used for operational risk in this study is asset volatility and for accounting conservatism, we use Ball and Shivakumar (2005) model [Ball, R., & Shivakumar, L. (2005). Earnings quality in UK private firms: comparative loss recognition timeliness. Journal of Accounting and Economics, 39(1), 83-128.], which analyzes accounting from balance sheet sight. The statistical society used in this study is taken from 15 banks in Tehran Stock Exchange over the period 2006-2012. The research result demonstrates that there was a negative relationship between operational risk and accounting conservatism. In other words, there is a significant negative relationship between operational risk and accounting conservatism. Hence, the results suggest that with an increase (decrease) in operational risk, accounting conservatism decreases (increases).