Immobilizing zwitterionic molecules on material surfaces has been a promising strategy for creating antifouling surfaces. Herein, we show the ability to surface derivatize an allylether-functionalized thermoplastic polyurethane (TPU) with a zwitterionic thiol in a radically induced thiol-ene reaction. The thermoplastic polyurethane was synthesized to have an allyl-ether side functionality using a modified chain extender molecule. The zwitterion surface functionalization was achieved via thiol-ene reaction in aqueous conditions. The presence of chemically tethered zwitterion moieties on the TPU surface was confirmed using X-ray photoelectron spectroscopy (XPS). Protein adsorption experiments via quartz crystal micro-balance (QCM) show reduced fibrinogen attachment for the zwitterion-derivatized TPU when compared to its nonfunctionalized controls. The Zwitterion-TPU also showed a log scale reduction in bacterial adherence. For Pseudomonas aeruginosa and Staphylococcus epidermidis, the Zwitterion-TPU resulted in around a 40 and 50% lower bacterial biomass accumulation, respectively, over the time scale of the experiment. The fibroblast cell viability of TPU remained unaffected by functionalization with zwitterion thiol. The results from our model experiments suggest that a zwitterion-modified TPU is a promising candidate for antifouling catheters.