The main objective of the present work was to study the effects of dispersion and distribution of the silica nanoparticles in ternary PP/EPDM/SiO₂ systems. Different morphologies were developed via applying different feeding orders (one-step or two-step) as well as alteration in functionality of the rubbery phase (EPDM or EPDM-g-MA). Morphological characterizations were performed using direct SEM observation and indirect dynamic-mechanical analysis. The results showed that the main toughening mechanism of the ternary systems was shear yielding of the PP matrix, while the corresponding binary reference PP/EPDM or PP/EPDM-g-MA blends underwent internal cavitation of the rubbery phases. This led to increased toughness and stiffness of the ternary blend-nanocomposites compared to the binary blends, representative of the synergistic effects of the soft rubber phase and the rigid silica nanoparticles. This synergy effect was much more obvious when the silica nanoparticles were preferentially localized around the rubber domains, leading to the overlapping of the stress fields within the PP matrix which, in turn, led to the formation of regular striations during impact testing. On the contrary, localization of most of the nanoparticles within the rubbery phase masked the stiffness and rigidity of the silica phase and, as a consequence, led to lower mechanical performance compared to other ternary systems.