In this study, Geographical Information System (GIS) - based Analytical Hierarchy Method (AHM) was used for constituting Multiple Criteria Decision Analysis model to select the most appropriate location for a new wastewater treatment plant located in Sarioglan District of Kayseri Province in the Central Anatolia, Turkey. Eight important criteria have been determined for optimum wastewater treatment plant sites. During the evaluation of these parameters, opinions of technical experts who have experience in sewerage systems, rainwater disposal systems and wastewater treatment plants together with those personnel working actively in public corporations have been benefited. Criteria-specified weights of all the eligible sites for the wastewater treatment plant at the south of the town emerged the most appropriate area of 33 hectares. The obtained results indicate the success of the multi-criteria decision analysis for finding the most appropriate location for the wastewater treatment plant. In addition to this process, binary comparison and multi-criteria decision can also be used in many other location analyses.