Enhancement of electrical properties of carbon fiber reinforced (CFR) epoxy matrix composites was aimed by incorporating varying amounts (0.5, 1, 2, 4, 7, 10, and 15 wt% - percentage by weight) of carbon nanoparticles (CNPs) into the resin [CNPs used were multi walled carbon nanotubes (MWCNTs) and graphene oxides (GOs)]. Besides, within these CNP percentages, MWCNT to GO composition ratio was also changed (100:0, 80:20, 50:50, 20:80, and 0:100) in order to investigate the synergy between these two type of CNPs. Carbon fiber/epoxy composites were produced via prepregging technique, followed by compression molding method. The change in electrical conductivity of the composites was examined in three directions: Fiber direction, transverse direction, and through-thickness direction. Additionally, mechanical property investigation was carried out by determining the interlaminar shear strength (ILSS) of composites by conducting short beam shear tests ( SBS). Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) analyses were performed for morphology investigation and element characterization of the CNP surfaces. The results revealed up to 5.8 (for 15wt% and 100:0), 217 (for 0.5wt% and 100:0), and 34 (for 0.5wt% and 20:80) fold increases in conductivity values in fiber, transverse, and thickness directions, respectively, when compared to that of the neat composite. For the thickness direction, the synergy between the NPs was obvious while some other high values were also achieved for other CNP compositions. Also, approximately 87% increase in ILSS value (for 0.5wt% and 100:0) was achieved by CNP addition.