This paper investigates the impact of the Civil War and the Easter Attack 2019 on the Hotel and Travel Sector, employing the Event Study Methodology that is widely used and free from deliberate interferences. The Market Model is applied to calculate the Expected Returns (R_it) by taking daily data for closing share prices of overall forty-one (41) listed companies under the Hotel and Travel sector in Colombo Stock Exchange by the particular event dates while the daily All Share Price Indices (ASPI) are considered as the market return (R_mt). The event timeline is specified considering 41 days' event window and 80 days before the event window for the estimation window. The market model is mainly based on the Ordinary Least Square (OLS) Method for estimating parameters. For analysing data, graphical analysis and t-test analysis are necessarily applied. This study concludes that terrorism is the event capable of creating an unfavourable impact on the value of the Hotel and Travel Sector companies. Especially, the Hotel and Travel Sector has provided no evidence for the semi-strong form efficiency. Further, the Hotel and Travel Sector of Sri Lanka has been adversely affected by Easter Attack 2019, collapsing the favourable economic condition developed for 10 years after the brutal Civil war. Ultimately, this study recommends getting an idea of how to upgrade the mechanism of an efficient market, which provides a platform for investors who trade securities to keep the Hotel and Travel Sector investment flow healthy and stable.