An efficient compatibilization system based on a combination of styrene-butadiene block copolymer (SBS) with ethene-propene random copolymer (EPM) has been developed for polyolefin/polystyrene blends. Model blends of polypropylene and polystyrene have been taken for compatibilization studies. Concentration of combined compatibilizer in all studied blends was 5 or 10 wt. %. The ratio of EPM/SBS in the compatibilizers was varied from 4/1 to 1/4. Tensile impact strength was used as the main criterion of compatibilization efficiency. Besides mechanical properties, basic morphological investigation of the prepared blends was carried out. The compatibilization efficiency of the EPM/SBS system in PS/PP blends depends on the type of blend matrix. Generally, the use of EPM/SBS leads to better or comparable mechanical properties of final polystyrene/polypropylene blends compared with those using common SBS compatibilizers.