Natural rubber (NR)-poly(ethylene-co-vinyl acetate) (EVA) blends have been studied by incorporation of mercapto-modified EVA (EVASH) combined with dicumyl peroxide (DCP) as a curing agent. The mechanical, thermal, and morphological properties of NR-EVA blends as functions of blend composition and compatibilizer and/or curative additions were investigated. An EVASH-DCP combined system leads to the greatest improvement in tensile strength when EVA is dispersed within the NR matrix. Higher performance on Shore A hardness was also achieved with this combined system. For blends characterized by NR domains dispersed in the EVA matrix, the efficiency of pure DCP in improving the tensile strength is higher. Morphological observations and selective extraction experiments indicate the cross-linking of NR phase in both systems. A cross-linking of the EVA phase is also suggested by DCP or an EVASH-DCP combined system, based on the decreasing degree of crystallinity of this phase.