Landfill site selection is a multi-attribute decision problem, through which factors like available land area, soil conditions, climatological conditions, and economic considerations are investigated in detail. Frequently, it is a challenge to come up with "the one" solution while tackling such complex systems. Therefore, use of tools such as fuzzy analytic hierarchy process (fuzzy AHP) and fuzzy technique for order preference by similarity to ideal solution (fuzzy TOPSIS) should be preferred in order to emphasize pros and cons for each of the studied options. In this study, three possible landfill sites for the city of Istanbul are evaluated through expert opinion and by facilitating fuzzy AHP and fuzzy TOPSIS. Initially, the landfill site selection problem is presented in the framework of a model and then the model is mathematically solved by calculating the individual criterion weights. In conclusion, considering the rapid rate of urbanization for the city of Istanbul, the possible landfill sites convey similar overall results, but differ in specific criteria.