The effects of hybrid carbon nanotubes (CNT) and graphite nanoplatelets (GNPs) on the mechanical and electrical properties of epoxy nanocomposites were studied. When the total reinforcement contents is fixed at 2wt.%, the nanocomposite containing 1% GNP and 1% CNT achieves the highest electrical conductivity of 4.7×10−3S/cm, which is more than two orders of magnitude higher than that of nanocomposites with 2wt.% GNP alone. Although the flexural properties are only marginally changed by hybridization, the quasi-static fracture toughness can be enhanced significantly by increasing the CNT content.