In this study, copper nanoparticles (CNPs) were applied to obtain optimized mechanical and electrical properties of copper nanoparticles/natural rubber composites cured through sulfur vulcanization. Moreover, the effect of both conventional and efficient curing systems, in presence of copper nano particles or without CNPs, on these mentioned properties was also compared. For this purpose, compounds including different contents of copper nanoparticles were prepared under the same processing condition considered for each sample preparation. The samples were cured by means of compression molding at constant temperature/pressure and specific time duration. The efficient cured samples containing 0.074 vol% of CNPs possessed the highest electrical conductivity (similar to 0.014 S m(-1)) at a percolation threshold and showed tensile strength around 12.79 MPa among different samples. SEM and TEM data revealed that homogenous dispersion and distribution were attained for the efficient cured samples reinforced with a considerably low amount of CNPs. (C) 2016 Elsevier Ltd. All rights reserved.