ABSTRACT: Weathering grades and their depths are some of the most important geo-engineering propertiesdetermining the cost, efficiency and sustainability of the engineering projects. Weathering properties of therocks should be clearly defined during the preliminary surveys of the studies on foundations, slopes etc. Asweathering properties are heterogeneous and anisotropic more boreholes are needed to increase theaccuracy of the interpretations of the subsurface. Electrical Resistivity Tomography (ERT) technique isused for different purposes to obtain faster and more economical data from wider area than drilling. Dueto such specialities of ERT, the technique was used for determining the weathering properties of thepyroxenites and dunites outcropping in Bursa region. ERT studies were carried out in three lines. Two- ofthe lines were on the dunites and the other line on the pyroxenite. Dunites in this study were observed fromunweathered to completely weathered stages, and the pyroxenites were observed from slightly tocompletely weathered stages. During ERT studies both dipole-dipole and Wenner configurations weredeployed. According to the data obtained, inversion model sections were generated. These sections wereevaluated regarding the changes in engineering properties of the dunites and pyroxenites. According to theevaluations, it is concluded that Wenner configuration especially for the dunites represents betterresistivity distributions for the weathering properties.