Multiwalled carbon nanotubes (MWCNT's) and Nano-Silicon dioxide (SiO2) reinforced HDPE composites have been developed. The MWCNT and Nano-SiO2 filler content was varied up to 5 wt% in HDPE with the addition of Polyethylene grafted glycidyl methacrylate compatibilizer and 3-aminopropyl triethoxy silane coupling agent. The dielectric and mechanical properties of the HPDE nanocomposites have been investigated in this study. Addition of MWCNT and Nano-SiO2 are observed to enhance the tensile strength and modulus of the nano-composites. The electrical properties like breakdown voltage and volume resistivity showed improvement with the addition of Nano-SiO2. (C) 2016 Elsevier Ltd. All rights reserved.