Isotropic conductive adhesives (ICAs) have drawn lots of attention in recent years due to their potential application in environmentally friendly microelectronic packaging. ICAs have numerous advantages over traditional Sn/Pb solder because ICAs require fewer processing steps and a lower processing temperature so that one can prepare heat-sensitive and low-cost chip carriers with fine-pitch capability.1 However, the high electrical resistivity and the poor mechanical properties of ICAs have been stumbling blocks.2 A novel method of improving the electrical conductivity of epoxy/silver nanocomposites by adding silica particles was explored experimentally and theoretically. Silica particles significantly decreased both the electrical percolation threshold concentration of silver nanoparticles and the electrical resistivity of the composite. They also enhanced thermomechanical properties, such as CTE. Molecular simulations demonstrated that effective intermolecular interactions between silver nanoparticles become more attractive with increasing the content of silica particles, aiding the formation of electrical percolation networks.