Surface-functionalization chemistries were optimized to tailor the surface chemistry of polyethylene, and this made covalent attachment of bioactive molecules possible. This concept has relevance in biomaterials, biosensors, textiles, and active food-packaging applications. Clean polyethylene films were subjected to chromic acid oxidation to introduce carboxylic acids. A range of functional groups, including amine, aldehyde, thiol, and hydroxyl, were then introduced to the surface of the oxidized films with functionalized crosslinking agents and covalent bioconjugation chemistries. The quantity of functional groups was further increased by subsequent grafting of polyfunctional agents such as polyethylenimine and poly (acrylic acid). The number and type of functional groups were quantified by contact-angle, dye-assay, attenuated total reflectance/Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. We optimized chemistries to introduce a variety of functional groups to the surface of low-density polyethylene in numbers ranging from several picomoles per centimeter squared to tens of nanomoles per centimeter squared. A range of bioactive compounds, including antimicrobials, antibodies, oligonucleotides, cell precursors, drugs, peptides, enzymes, and synthetic biomimetic agents, can be covalently bound to these functional groups in the development of nonmigratory biofunctionalized polymers.