The reactive compatibilization of ethylene-propylene-diene (EPDM)-based dissimilar elastomer blends has been performed using mercapto-functionalized copolymers. The mercapto groups are able to react with the double bonds of the high diene rubber, resulting in a good Interaction between phases. The mechanical properties of natural rubber/EPDM blends were significantly improved by the addition of 2.5 phr of mercapto-functionalized EPDM (EPDM-SH). Blends composed by nitrile rubber with EPDM displayed good results in terms of mechanical properties when mercapto-functionalized EVA (EVA-SH) was employed instead of functionalized EPDM, probably because of the higher polarity of the former associated to its lower viscosity. Additionally, an improvement on mechanical properties was also achieved by using EVA-SH in combination with nitrile rubber functionalized with epoxy or oxazoline groups.