The physical properties of difunctional epoxies would be improved by adding nanofillers and multifunctional epoxies. Therefore, in this study, a tetrafunctional epoxy was added to difunctional epoxy/GNPs nanocomposites. An aminosilane was used to improve the interfacial bonding between GNPs and the epoxy matrix. The physical properties of the epoxy/GNPs nanocomposites were investigated by DSC, TMA, DMA, and electrical resistivity test. The glass transition temperature and storage modulus of the nanocomposites increased with increasing GNPs content. Adding the aminosilane resulted in a marginal increase in the glass transition temperature of the nanocomposites. However, adding the tetrafunctional epoxy resulted in a considerable increase in the glass transition temperature, thermal dimensional stability, and storage modulus of the nanocomposites. SEM images of the fracture surfaces of the nanocomposites showed that the aminosilane improved the interfacial bonding. The aminosilane and tetrafunctional epoxy made the sheet resistance of the nanocomposites higher. The sheet resistance data showed electrical percolation at 1-2 phr of GNPs. POLYM. ENG. SCI., 54:969-976, 2014. (c) 2013 Society of Plastics Engineers