In this work we present a comparative study on the efficiency of surface modifications of Copper/Polystyrene (Cu/PS) nanocomposite films, induced by N2 DC plasma and gamma radiation to enhance their surfaces' antibacterial activity. Cu/PS nanocomposite films, with different concentrations of copper 0.4, 0.8 and 1 wt.%, were prepared by the solution casting method at room temperature. The samples were exposed to gamma with different radiation doses and N2 DC plasma for different treatment time. The structural and morphological properties of the samples were investigated before and after treatment by, water contact angle measurements, weight loss and scanning electron microscopy. The surface of the films were found to be more sensitive to N2 DC plasma than gamma radiation. The antibacterial properties of Cu/PS nanocomposite films against Staphylococcus aureus 15 have been evaluated by the optical density and colony forming unit's techniques. The results indicated that the N2 DC plasma treatment enhanced the antibacterial properties more than gamma radiation.