Surface modification of argon plasma-pretreated low-density polyethylene (LDPE) film via UV-induced graft copolymerization with a fluorescent monomer, (pyrenyl)methyl methacrylate (Py)MMA, was carried out. The chemical composition and morphology of the (Py)MMA-graft-copolymerized LDPE [(Py)MM2A-g-LDPE] surfaces were characterized, respectively, by X-ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The concentration of the surface-grafted (Py)MMA polymer increased with Ar plasma pretreatment time and UV gran copolymerization time. The photophysical properties of the (Py)MMA-g-LDPE surfaces were measured by fluorescence spectroscopy. After graft copolymerization with the fluorescent monomer, the surface of the LDPE film was found to have incorporated new and unique functionalities.