Foreign Institutional Investors (FIIs) have been gaining importance in the Indian stock market in the last few years. As the Indian stock market is integrating with the world’s stock markets FIIs have become one of the major players in the Indian stock market. FIIs flows will continue to be a major influence on the Indian stock market. The study has attempted to test the impact of FIIs monthly net flows on Nifty index. This study is descriptive one based on the secondary data is used for conducting this research. The data is analyzed using statistical tools like, Correlation and Regression. The dependent variable is Nifty index, and the independent variable is FIIs monthly net flows. The broad conclusions are drawn. The Correlation techniques have revealed that FIIs monthly net flows and Nifty index are highly positively correlated except in one period. Regression results infer that FIIs monthly have a significant impact on both the Nifty index. The study provides suggestions to the investors, FIIs brokers and the regulators. The study thus corroborates the views that FIIs are going to be the major players in the Indian stock market in the future. Keywords: Foreign Institutional Investors, Stock Market, Nifty, Correlation, Regression