The exceptional and distinctive properties of the allotropes of carbonaceous nanomaterials like carbon nanotubes and graphene have attracted many researchers and engineers to enhance the performance of fibrous polymeric composites. This article extrapolates the synergetic impact of carbon nanotube (CNT) and multi-layered graphene (MLG) reinforcement onto the mechanical performance of glass fiber/epoxy composites. Magnetic stirring and ultra-sonication process have been carried out under optimized parameters for incorporation of CNT-MLG into the epoxy polymer. Incorporation of 0.1wt% of carbon nanotube to the glass fiber/epoxy composites enhances a flexural strength of 10% and addition of 0.1 wt. % of multi layered graphene to the glass fiber/ epoxy composites enhances a flexural strength of 6% when differentiated with neat GE. Embodiment of 0.1 wt. % CNT and MLG to the glass fiber/epoxy composites in three different ratios like 1:1, 1:2 and 2:1 showcases a 13%, 12.25% and 14.7% enhancement in the flexural strength respectively with respect to the neat glass fiber/epoxy composites when tested at room temperature. Among them, the ratio 2:1(CNT: MLG) contributes higher strength due to the combined action of high aspect ratio of CNT and higher specific surface area of multi-layered graphene thus, facilitating efficient stress transfer from matrix to the reinforcements. Thermal characterizations have been carried out using differential scanning calorimetry (DSC). The fractography of the samples is examined through the scanning electron microscope. © 2020 Trans Tech Publications Ltd, Switzerland.