Safety evaluation is a fundamental stage of existing dams and their appurtenant structures, which have a high-risk potential for downstream life and property. Turkey is a country, which seismically settled at one of the most active regions in the world, and earthquakes with high magnitude frequently occur here. There are some regions, which are severely under threatening of earthquakes. One of them is the Marmara region with twenty-four million people. This region, namely the Marmara basin, has at least forty-five large dams with different types. This study considered nineteen of them to relieve their seismic hazard parameters for all dam sites and total risk for each structure. The study area is lying in a seismically, very active part of Turkey. The southern part of the basin is structurally cut by the North Anatolian Fault, which is a famous structural feature that produces deathful earthquakes, and its offshoots. The analyses have indicated that peak acceleration widely ranges for the nineteen dam sites of this basin. The total risk analyses have concluded that most of the dams in the metropolitan area have high-risk classes and a significant effect for public safety.