Strength characteristics of rock are very important parameters for rock mass classification and design of structures either upon or inside rock. A petrography study is crucial for a better understanding of the alteration faces and its mechanism. The petrographic characteristics of rocks have a constructive effect on the macro-mechanical properties and especially on rock strength. Mineral composition, grain size and microstructure are the most important parameters to influence the rock strength and deformability. In this study, the collected samples were subjected to petrographic analyses and physico-mechanical tests fromYakakayi dam site located 25 km far from northern part of Eskisehir city. The rock units at the dam site are ophiolitic rocks of Upper Cretaceous in age and terrace, talus and alluvium of Quaternary age. The most important engineering characteristic of rock material for rock characterization and design is its intrinsic strengthwhich is directly determined by uniaxial compression strength test. The aim of this study is to determine the engineering, petrography, slake durability properties of ophiolitic rocks at Yakakayi dam site. The laboratory test results indicate that the mean uniaxial compressive strength value of ophiolitic rocks as basalts is 63.02MPa, limestones is 15.69MPa, radiolarians is 28.37MPa and serpentines is 13.47 MPa. Also, slake durability index properties of ophiolitic rocks are in high class. Therefore, no problem is expected regarding of durability and porosity at the dam site.