Surface properties of blends prepared of styrene-acrylonitrile and ethylene-propylene-diene changing the homopolymer proportions and compatibilized by high impact polystyrene have been studied by contact angle measurement. The surface free energy of interphase of homopolymers pairs, work of adhesion, and wetting coefficient were calculated using Wu's geometric mean method and the total surface free energy and acid-base components of the blends by using van Oss, Good and Chaudhury method. Blends were also characterized by dynamic mechanical analysis and by scanning electron microscopy. The miscibility of studied blends was estimated through changes of surface free energy, energy of interface and through the shifts of glass transition temperature and changes in morphology. From the results, it can be seen that added compatibilizer reduces the interface energy and provides more homogenous system by interfacial segregation and rearrangements of molecules at the blend surface. The results of morphological observations reveal that the addition of a small percentage of compatibilizer decreases the domain size of the dispersed phase and enhances the compatibility of the blends.