Numerous works have been reported in order to enhance the barrier properties of the polystyrene (PS). In this work, hydrophilic graphene oxide (GO), prepared by the Hummer method, was surface-grafted with hydrophobic poly(4-vinylbenzyl chloride), p(VBC), via in situ radical polymerization approach. The graphene oxide/poly(4-vinylbenzyl chloride), GP(VBC), was then dispersed in the polystyrene matrix in order to obtain nano-composite thin films of different filler ratios (5, 10, 15, 20, and 25) wt%. The modified GO and its corresponding films were characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscope, field emission scanning electron microscope, thermal gravimetric analysis, and contact angle. Mechanical properties of the films were studied as well. The results indicated that the surface modification step improved the dispersion of GO within the polystyrene film due to the hydrophobic nature of modified GO. Consequently, an obvious enhancement of thermal stability and mechanical properties of the PS films loaded with GP(VBC) compared with the pure films was noticed. The rate of water vapor permeability showed an abrupt decrease even at the lowest loading percentage of the filler, which is 5 wt%. The antimicrobial activity of the fabricated polystyrene nano-composite films was also investigated against deleterious pathogens. As a net result, the composite films revealed superior properties thanks to the inclusion of the GP(VBC). This present work paves the way for the next generation of high barrier and bactericide polystyrene packaging with an economic impact.Graphical Abstract