Many factors affect stock market price behaviors; they bring out over-or under-reaction in the market. This study intends to find the impact of major catastrophic event on stock returns. For this purpose, it uses daily data of stock prices with total 210 observations and the impact of catastrophic event (Nepal Earthquake 2015) is tested for different event windows using the event analysis methodology. The catastrophic event doesn’t seem to have significant impact on stock returns and is resilient to shocks caused by earthquake. The study shows that Nepalese stock market is inefficient at a semi-strong level. Results also demonstrate the higher abnormal returns in the event window of (+2, +10)