Nanodiamonds (NDs) and graphite nanoparticles (GNPs) offer vast range of distinctive features like electrical conductance, heat tolerating capacity and super mechanical attributes in polymer matrix, adjustable surface morphology and highly stable inert core. However, these nanoparticles are highly inclined towards cluster formation in solution due to their high surface energy. This research work focuses on the dispersion and disintegration of nanoparticles in epoxy matrix after neumrous surface treatments in order to polish their masked properties. Moreover UV/ozone method and acid refluxing were applied to treat the surfaces of NDs and GNPs, respectively, to reduce surface agglomeration and increase uniform dispersion of nanofillers in matrix phases. Seven different samples including (pure epoxy, 0.1, 0.3 and 0.5 wt% GNPs/epoxy and hybrid GNPs–NDs/epoxy) were evaluated for mechanical properties in terms of break strain, tensile strength, flexural strength and shore hardness. Tensile properties of the prepared nanocomposites, in terms of tensile strength, tensile toughness, tensile modulus and elongation to break, gave tremendous outcomes. Stress–strain study also proved very beneficial to evaluate different epoxy nanocomposite’s performances. Thermal conductivity and thermogravimetric analysis for these nanocomposites were also found remarkable. It was observed that 0.3 wt% amount of nanofillers (GNPs–NDs) in reinforcement phase was found to be the best for achieving the magnanemous mechanical as well as thermal attributes.