Reusing of the wastewater has a vital importance because of limited natural water resources all around the world. Recycled wastewater can be used in many areas such as agriculture, industry, cleaning etc. Treatment of wastewater is one of the important tasks of metropolitan municipalities. The aim of this study is to evaluate the performances of wastewater treatment services provided by the metropolitan municipalities in Turkey using a hybrid approach using Entropy, SAW, MOORA and TOPSIS methods. In the scope of the study, four criteria have been considered as the ratio of the municipal population served by the treatment plant to the total population, the ratio of the municipal population served by the sewerage system to the total population, treatment rate of discharged water, increase rate of treated water in treatment plants. A case study has been conducted in Turkey and the metropolitan municipalities have been ranked depending on their performance. Aydin Metropolitan Municipality as the highest municipality and Kahramanmaraş Metropolitan Municipality as the lowest municipality have been determined. In Western cities performance is high, performance goes down as it goes east.