Ethylene propylene diene rubber (EPDM) and styrene butadiene rubber (SBR) blends were compatibilized by a graft copolymer EPDM-graft-styrene. This compatibilizer was prepared by gamma radiation induced grafting of EPDM with styrene monomer. The compatibilized blends were evaluated by scanning electron microscope and dielectric properties. The obtained results reveal that the addition of a small percentage of graft copolymer to EPDM/SBR blends improves the physico-mechanical properties of the blend vulcanizates, and this can be related to the enhancement of the blend compatibility.