The impact strength and crystallite structure of un-vulcanized and dynamically vulcanized polypropylene/ethylene-propylene terpolymer (PP/EPDM) blends and polypropylene/ethylene-propylene terpolymer/carbon nanotube (PP/EPDM/CNT) blend nanocomposites with and without maleic anhydride-grafted polypropylene (PP-g-MA) were studied. The results showed that incorporation of EPDM increased the impact toughness of PP matrix by promoting debonding and cavitation of rubber particles. Dynamic vulcanization increased the interfacial adhesion leading to superior impact strength. Incorporation of CNT into PP/EPDM blends changed the crystallization behavior of the PP matrix and further increased the impact resistance. Morphological observations on impact-fractured surfaces indicated that dominant failure modes of CNTs in blend nanocomposites with and without PP-g-MA are pulling out and breakage of nanotubes, respectively. While the PP-g-MA had a negative effect on the impact strength of PP, the results demonstrated that its presence enhanced the impact strength of the blends and blend nanocomposites mostly via enhancing the adhesion between the PP and EPDM particles and improving the dispersion of CNTs in the matrix, respectively. The former decreases the rubber particle size and the latter decreases the size of CNT aggregates and crystallites.