The zinc-sulfonated EPDM (SEPDM)-epoxidized natural rubber (ENR) blend is self-crosslinkable in the sense that it undergoes crosslinking on molding at high temperatures without the aid of any external curing agents. This is evident from Monsanto rheometric, solvent swelling, and infrared spectroscopic studies. The sulfonate anion is believed to react with an epoxide ring, leading to the formation of sulfonate ester and ether crosslinks. The extent of crosslinking depends on the degree of sulfonation of SEPDM and epoxidation level of ENR, the blend ratio, molding time, and temperature. Dynamic mechanical analyses of the blends show the immiscibility of the blend components. The chemical interaction is also manifested in the shift of the glass transition temperature of ENR to the high-temperature region.