Plasticity index is one of the most important parameters affecting the behavior of fine-grained soils under monotonic and dynamic loads. Besides, various correlations between plasticity index and strength properties of fine grained soils can be obtained depending on loading type, drainage, and loading rate conditions. In this study, mechanical properties of soils with different plasticity index prepared by mixing kaolin and montmorillonite clay at various ratios were investigated. Atterberg limits and unconfined compression test were performed on the obtained mixed soils. Firstly, Atterberg limit values of specimens prepared with at 10, 20, 30, 40 and 50 % montmorillonite replacement level were obtained. According to the determined Atterberg limits, specimens with different liquidity index were subjected to unconfined compression tests. The unconfined compressive strengths of the specimens are analyzed according to the percentage of different clay minerals and liquidity index also the relation between these parameters were explained. Significant decreases in the unconfined compressive strength have been observed with the increase in montmorillonite clay contents. Besides, the strength of specimens decreased when the liquidity index value of the prepared samples increased from 0 to 1.