Polyurethanes (PUs) with soft blocks containing semifluorinated (-CH2OCH2CF3) and 5,5-dimethylhydantoin pendant groups were prepared and employed (2 wt%) as biocidal polymeric surface modifiers (PSMs) for a conventional PU coating comprised of an isophorone diisocyanate/1,4-butanediol-derived hard block (50%) and poly(tetramethylene oxide) soft block. Surface enrichment of the PSM was verified by dynamic contact angle measurements. The PSM modified PU was activated by converting near-surface amide groups to chloramide with 3wt% hypochlorite. The conversion of near-surface amide to chloramide is reflected in somewhat increased hydrophobic character for the antimicrobial chloramide functionalized surfaces. Biocidal activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, and Escherichia coli) bacteria was demonstrated by using a modified version of American Association of Textile Chemists and Colorists (AATCC-100) test. By changing the PSM concentration it was found that only 1.6 wt% PSM (0.66 wt% biocide, 5,5-dimethylhydantoin) in a conventional PU affected complete kill of P. aeruginosa in 15 min by using this biocidal testing protocol.