Nanoparticles could improve the mechanical properties of polymer based composites due to synergy of higher filler-matrix interaction and better load transfer from matrix to the fillers. Epoxy resin has high strength and modulus, and good adhesion strength, which makes it attractive for several industrial applications. To improve interfacial bonding between epoxy and silicon dioxide (SiO2), surface treatment of SiO2 is done using acetone and silane coupling agents. To improve SiO2 dispersion in epoxy matrix, the epoxy matrix is modified by mixing with amine containing liquid rubber. Ultrasonication process has been used for uniform mixing of SiO2 in the modified epoxy resin. Carbon fabric reinforced epoxy (CF/Ep) composite with surface treated nano- SiO2 are fabricated using vacuum bagging technique followed by hot press. The effect of silane treated nano- SiO2 with varying filler loadings from 0.5 to 3 wt% on the static mechanical properties such as hardness, tensile, and flexural properties are characterized following ASTM standards. The experimental results show that the inclusion of silane coupling agent increased the interfacial bonding between nano- SiO2 particles and the epoxy resin so that the surface hardness, tensile and flexural properties are improved.