In this study, the flexural strength and the impact behavior of the glass fiber composite plates with the same mesh and layer geometry and the effect of the addition of nanographene (GNP) at various ratios into the matrix were experimentally investigated. The variable examined in the study is the percentage of the nanographene that added in the matrix of glass fiber composite plates. In this study, six types of glass fiber plates were produced; with no nanographene added reference specimen, and with the ratio of 0.15, 0.25, 0.35, 0.45, and 0.70% nanographene added specimens. The effect of nanographene addition to the epoxy matrix on the flexural strength and impact behavior of the specimens was investigated by applying a three-point bending test and a constant-energy impact load with the free-weight test method on the glass fiber plate specimens. The highest flexural strength was observed at the 0.25% nanographene added specimen. Further addition of the nanoparticle caused the flexural strength to decrease. In the free weight drop impact test, the highest acceleration and lowest displacement were found at the 0.25% nanographene added specimen. Adding more nanoparticles adversely affected the impact behavior. The optimum nanographene ratio was determined to be 0.25%. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineers