Polystyrene (PS) is one of the most widely used thermoplastic polymers and is often not recycled because of its light weight and low scrap value. The discarded PS in landfill sites has limited capacity for water absorption, and physical and chemical properties that make it relatively inert. To increase wettability and introduce oxygen-containing functional groups, PS was treated at room temperature with ozone in the absence of the UV radiation which was used to make the ozone from the photodissociation of oxygen. X-ray photoelectron spectroscopy detected the increase of oxygen content on the PS surface and the formation of functional groups with reaction time. Advancing contact angle measurements showed an increase of hydrophilicity with treatment time. The superabsorbent polymer poly(acrylic acid) was partially and/or thinly grafted onto the modified PS surface.