Nanocomposite thermoplastic olefins have received great industrial and academic interests. All processing characteristics and mechanical properties of these materials are governed by the micromorphology specially the size, shape and dispersion state of the rubber droplets. Incorporation of a nanofiller allows controlling the viscosity ratio and hence microstructure of the materials. In the present work attempts have been made to investigate the role of the type of interfacial compatibilizer and sequence of mixing process upon the microstructure, melt processing characteristics as well as mechanodynamic properties of thermoplastic olefin nanocomposites prepared by melt compounding of polypropylene (PP), ethylene–propylene–diene monomer (EPDM) and nanosilica. For this purpose, maleated PP (PP-g-MAH) and maleated EPDM (EPDM-g-MAH) were used to control the affinity of SiO2 particles toward the PP and EPDM phases. Moreover, nanosilica was incorporated in the form of both masterbatch and direct on to the mix. Field-emission SEM (FE-SEM) revealed that incorporation of SiO2 via masterbatch mixing is much beneficial in formation of rubber droplets with average size of less than 1µm with interparticle distance within few micrometer. These were evidenced by significant increase of impact resistance parallel with enhance elastic modulus. PP-g-MAH showed to be more effective in reducing the rubber droplets size, indicating the preferential residing of nanosilica in the PP matrix which leads to the reduction of viscosity difference between PP and EPDM phases. Melt reheological studies did also show increase in melt viscosity with nonterminal characteristics for both groups of TPO/Silica nanocomposites generated by PP-g-MAH and EPDM-g-MAH, indicating the presence of high relaxation times as a result of retardation of segmental motions by the SiO2 physical networks. Dynamic mechanical thermal analysis (DMTA) performed on nanocomposites exhibited less damping characteristic for the