Mergers and acquisitions are being used as strategic tools by Indian Corporate houses especially by Indian banking sector during last three decades of post liberalization era. Banking Sector in India has witnessed a mega merger of 10 Indian public banks into four big banks with effect from 1st April 2020 which definitely attract attention of different stakeholder who are interested to know whether these tie up events are really helpful for improving present scenario of banking industry as well as economic condition of the country in long run. But our concern in this study is to figure out the changes that occurred in shareholders wealth of the acquiring firm in short run around the announcement of merger event by detecting the responses of the share prices of acquiring bank through the procedure of event study methodology. For this study, company specific and market specific secondary data have been collected from the official website of National Stock Exchange as these companies are actively traded on said exchange. To accomplish the objective of this study we relied on figure of Average Abnormal Returns (AAR) and Cumulative Average Abnormal Returns (CAAR) for an event window of 41 days from day -20 to day +20. Return values have been statistically tested through cross sectional t-test. The notable finding of the research is that an under-reaction of market is observed before the announcement but the moment the announcement information becomes effective, investors start reacting from day +2 and the stock price jumps up, providing positive AARs to the investors. But after the positive respond to the merger information, finally investors have under-reacted to the event. CAARs figures also indicate the positive pattern of returns in the beginning of the event window but rapidly it becomes negative from day -16 to the last day of window that might be due to pandemic situation running throughout the world. KEYWORDS: Merger & Acquisition, Event Study, Stock Return, Abnormal Return, Banking Sector