Abstract The foreign institutional investments have become an important factor impacting the stock market volatility. The fluctuations in the stock market(SM) affect the returns of the investors. Also one of the reasons of fluctuation is foreign institutional investments. This study is an aim to find the impact of FIIs on the Bombay Stock Exchange (Sensex). BSE is the oldest stock exchange of India and ranks 10th in term of market capitalization in the world. The tools used in the study is Augmented Dickey Fuller test to study the stationarity of the time series and the GARCH model has been used to study the impact of the FIIs on the volatility of the BSE-Sensex. The phase of the learn is from January 2015 to December 2019. Monthly information have be taken on behalf of research. The research study outcomes revealed that the FIIs have very important impact on the volatility of SM i.e. Bombay Stock Exchange- Sensex