Silicone rubber (SiR) and Ethylene propylene diene monomer (EPDM) are broadly employed polymeric materials used in high voltage (HV) insulators. Both have their advantages and disadvantages regarding to mechanical and electrical properties. One of the major advancements of a novel polymer insulator having excellent properties is blending them. The main advantage of such a process is that the intermediate properties are sometimes superior to those of either of the single components. The combination with inorganic nanofiller has been used to improve the existing properties of the blending. In this study, for SiR/EPDM composite with different blending ratios, nanofiller Silica (SiO2) with (1,3,5, and 7) Phr have been added using a two-roll mill. SiO2 was selected as the filler material since it has excellent reinforcement, outstanding dielectric characteristics, and better thermal stability. The impacts of the nanofillers on the dielectric strength and volume resistivity were investigated for assessing the electrical properties. Also, the mechanical properties like tensile strength and elongation at break were determined. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are performed. The experimental findings showed that the doping of nanofillers consistently enhanced the electrical and mechanical properties. The greatest improvement at 5 Phr of nano SiO2 for all SiR/EPDM composite samples. Additional nano-sized particle inclusion led to deteriorating electrical and mechanical properties.