Abstract Antimicrobial polyvinyl chloride (PVC) plastic was obtained by covalent bonding of poly hexamethylenediamine guanidine hydrochloride (PHMG), a guanidine based antimicrobial polymer. This was achieved by grafting mercaptopropyltrimethoxysilane onto PVC, followed by aminopropyltriethoxysilane. Glutaraldehyde is a bifunctional crosslinker that was bonded to the free amine groups found in the treated PVC on one side and PHMG on the other. The treated PVC samples were characterized by FT-IR and XPS, showing that the PVC samples were successfully modified. Energy Dispersive X-ray spectroscopy showed the spatial distribution of the elements Si and S, indicating that the coatings were homogeneous. The resulting PVC samples showed high antimicrobial activity against Gram-positive and Gram-negative bacteria. Furthermore, the biofilm formation was negligible in comparison with the untreated material. The coating elusion assay indicated that its antimicrobial ability was achieved via direct contact rather than a controlled release mechanism.