This paper shows that terrorist attacks have a wealth effect on stock market performances. Using the G20 countries as sample countries, this paper examines the wealth impact of the terrorist attacks on the stock market indices of these countries for the period 2010-2019. The objective is to find the relationship of the terrorist attacks on the wealth effect and informational efficiency of such events. The result shows the stock market performances decline significantly on the event day and continue to decline on the following day. This paper also further analyzes the impact of terrorist attacks on the Islamic countries and non-Islamic countries within G20 and document that the Islamic countries had a better wealth effect compare to non-Islamic countries. The informational efficiency of the events was better in the non-Islamic countries.