This article investigates the miscibility of nylon 66 and santoprene blends. The nylon 66-santoprene was blended to give the following compositions : 100/0, 90/10, 75/25, 50/50, 25/75, and 0/100. No compatibilizer was used during blending of the two components. Thermal properties and morphology of the blends were checked by using differential scanning calorimetry and scanning electron microscopy (SEM). The effect of blend composition on the mechanical properties was checked through tensile and izod impact tests. Both components were immiscible, as confirmed by double melting temperature, corresponding to that of polypropylene component in santoprene and nylon 66. Also, the melting temperature of nylon was not significantly affected by blending it with santoprene. However, the crystallization temperature of nylon increased after blending. This was attributted to the ethylene-propylene-diene monomer content in santoprene, which acts as a nucleating agent. The effect of blend composition on mechanical properties occurred at the 50/50 composition and above. Evidence of immiscibility of both components was also confirmed by the presence of a two-phase structure, as revealed by SEM.