Just like in other industries, it is very important to choose the best possible location in hotel investments. As there are too many alternatives and changing touristic demands, there is serious competition within the hospitality sector. Therefore, all the investors want their properties located at the most profitable and competitive sites. To do so, they should decide the hotel location site by doing a well-analysed feasibility study. The hotel location selection can be influenced by some elements such as natural, economical, socio-cultural, legal, psychological factors and agglomeration effects. All of these factors have important roles of a hotel’s business success. However, especially in the last few years, the increasing numbers of hotel investments call in doubt that these factors are not considered properly. With this doubt, the main problems of this research have been revealed: what main factors do the investors consider in their investment decisions, and how do they decide the best site to locate the hotel? These problems also create the aims of this paper, which are to determine the factors that are important for investors and to find out where the most selected investment zones are. To achieve this goal, Istanbul has been divided into five agglomeration (investment) zones such as Historical Peninsula, Taksim-Beşiktaş-Şişli, Sarıyer-Maslak-Levent, Airport Area and Anatolian Side, according to their agglomeration effects. Then, interviews were completed with six hotel investors from these areas in order to get their opinions about the investment decisions. The gathered information has been analysed by the fuzyy TOPSIS method, which helps to calculate the subjective thoughts of the investors in a quantitative way. Then, the order of preference within the investment zones was calculated to determine the most popular site among the investors. The results showed that the most important factors for hotel location selection are agglomeration effects and economical factors. According to the order of preference, the most preferred location site has been determined as the Historical Peninsula, which includes Fatih, Eminönü, Sultan-ahmet and Topkapı zones.