A green photoinduced method for the modification of a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), has been successfully carried out using three types of monomers with potential antibacterial effects, i.e., 2-[(methacryloyloxy)-ethyl] trimethylammonium chloride (META), 2-[(methacryloylethyl)]-dimethyl-(3-sulfopropyl) ammonium (MESA) and 2-hydroxyethyl methacrylate (HEMA). The photografting process is conducted through a photoinduced free radical process employing a ketone-based photoinitiator in an aqueous medium. Under appropriate conditions, the photogenerated radicals abstract hydrogen atoms from the PHBHV backbone, thus initiating the UV-mediated photopolymerization of derived-(meth)acrylate monomers from the surface of PHBHV film. The photochemical mechanism of the ketones photolysis is entirely described by a electron spin resonance/spin trapping technique, and the modified-PHBHV films are extensively characterized by ATR-FTIR and water contact angle and XPS measurements. Finally, a primary investigation is conducted to support the antibacterial activity of the new functionalized biomaterial against Escherichia coli and Staphylococcus aureus.