Three dimensional (3D) glass fiber epoxy composites reinforced with nano-SiO2 particles at ratios of 0.5 wt.%, 1 wt.%, 2 wt.% and 3 wt.%, were manufactured using the vacuum infusion method to improve the mechanical properties. Differential scanning calorimetry, thermo-gravimetric analysis, particle dispersion detection by color measurement, scanning electron microscopy, energy dispersive X-ray spectroscopy mapping, three point bending and tensile testing were performed to characterize the nano-particle-reinforced 3D composites. Mapping and color measurement revealed good dispersion of the nano-particles. The mechanical tests showed improvement rates of 52 % and 64 % respectively on warp and weft directions compared with the non-reinforced 3D composite. The tensile strength of the nano-SiO2 reinforced 3D woven composites also increased to 6 % and 10 % according to the warp and weft directions compared with the non-reinforced 3D composite.