Turkey experienced an extreme political event on Friday July 15 2016 in the form of an attempted coup. This paper examines the impact of this event on the components of the Banks Index of the Istanbul Stock Exchange using event study methodology. Results show that the banks’ abnormal returns (ARs) were a statistically significant negative from +2 to +6 days with the peak on day +3 when the government declared a state of emergency. Furthermore, when the banks’ stocks are compared with the overall market, they display lower volatility during the study period. These findings evidence the importance attached to political factors and particularly political instability in shaping investment decision making.