There is an urgent need for biocompatible and antimicrobial surfaces for biomedical devices to face the rapid spread of antibiotic resistance, the high risk of infection, and the formation of biofilms on implants. Antimicrobial peptides are promising candidates due to their broad spectrum of activity and cytocompatibility; however, they are limited by rapid enzymatic degradation. Peptoids are synthetic oligomers structurally similar to peptides, but have intrinsic resistance to proteolysis. In this work, the peptoid GN2-Npm9 was employed to functionalize a chemically pre-treated (CT) Ti6Al4V surface intended for bone-contact dental or orthopedic implants. Physicochemical characterization was performed through contact angle measurements, zeta potential titration, XPS analysis, and fluorescence microscopy. Based on chemical–physical characterisation, the peptoid adsorbed layer on CT was confirmed to be stable and homogeneous, mediated by electrostatic interactions. The modified surfaces were highly hydrophilic (contact angle ≈30°) and demonstrated sustained peptoid delivery over at least nine days. Based on the biological characterization, functionalized samples significantly inhibited colonization and biofilm formation by Escherichia coli, Staphylococcus epidermidis, oral plaque pathogens, and Pseudomonas aeruginosa. Antibacterial action was shown to be selective with both direct and quorum-sensing-mediated effects. Cytocompatibility with human mesenchymal stem cells was preserved, and co-culture models confirmed the protection ability of the functionalized surfaces on cells in the presence of bacteria.