The objective of this study is to understand the significance of graphene oxide type for the improvement of mechanical properties of carbon fiber reinforced epoxy composites. Modified epoxy systems were prepared by adding two different graphene oxide nanoparticles prepared by the modified Hummers method (GOH) and Laachachi method (GOL). In the second stage, carbon fiber reinforced epoxy composites were produced using prepreg manufacturing technique. X-ray Photoelectron Spectroscopy characterizations of the pure graphene and modified graphene nanoparticles (GOH and GOL) were performed to confirm the oxidation of the nanoparticles. The morphology of the nanocomposite epoxy resin was investigated with scanning electron microscopy. Mechanical tests were conducted with composites to determine the properties of the final materials. It was observed that the addition of the GOH improved the longitudinal tensile and flexural strength values by 41 and 33%, respectively. Interlaminar shear strength (ILSS) values of epoxy/carbon fiber significantly increased up to 58% with GOH addition. Moreover, the results show that nano-enhanced resins could be a key component for many composites, and it can be a suitable material for long term usage and resistance of sudden failure of composites.