Regardless, the advantages of packaging paper and paperboards they lose their marketing share to the plastics because of their inadequate barrier properties due to their porous structure. They have no resistance against gases, moisture, and vapors. For that reason, the aim of this study is imparting roughening to cellulose fiber surface by applying ultra-thin coating of PS /silica nanocomposite. The effect of hydrophobic coating on surface morphology (SEM), contact angel, water vapor permeability (WVP), water sorption isotherm, and mechanical properties were investigated. The maximum contact angel >120o was obtained at SiO2 nanoparticle concentration (4%). WVP results revealed remarkable sharp decline in WVP of coated paper compared with uncoated one with increasing coating thickness beyond ( 4% ) SiO2 nanoparticle content attained WVP (0.0003 g Pa-1 s-1 m-1) compared with uncoated sample (0.0126 g Pa-1 s-1 m-1 ). The sorption isotherm of PS/ silica nanocomposite coated paper results have been fitted using BET model. The curves exhibited the characteristic sigmoid-shaped type II isotherm. The monolayer water content values (M0) range between 0.00005 - 0.00280 g water/g dry film. The applied PS/silica nanocomposite on mechanical properties showed enhancement in each of burst, short span, tensile strength. However, roughness and elongation decreased further than (4%) SiO2 nanoparticle content.