In this study; a polymer composite was produced by adding different proportions of polystyrene (PS), styrene ethylene butadiene styrene thermoplastic block copolymer (SBS) and montmorillonite nanoclay into low density polyethylene (LDPE). Six different polymer composites were produced by mixing all materials in a twin screw extruder. Later, standard test samples were molded from the obtained polymer composites by injection molding method. To learn about the various mechanical properties of polymer composite materials obtained; tensile, three point bending, hardness, impact tests were conducted to obtain information about the various mechanical properties of the composite. In addition, in order to see the distribution of nanoclay powders in the matrix, photographs of the broken surfaces obtained from the impact tests were taken with scanning electron microscopy (SEM). According to the results of the tests, with the increase of nanoclay powder ratio in the matrix; elasticity modulus, tensile strength, flexural modulus, maximum bending strength and hardness values were increased but % elongation, impact strength and bending elongation values were found to decrease.