Prevention of biofouling and microbial contamination of implanted biomedical devices is essential to maintain their functionality and biocompatibility. For this purpose, polypept(o)ide block copolymers have been developed, in which a protein-resistant polysarcosine (pSar) block is combined with a dopamine-modified poly(glutamic acid) block for surface coating and silver nanoparticles (Ag NPs) formation. In the development of a novel, versatile, and biocompatible antibacterial surface coating, block lengths pSar were varied to derive structure property relationships. Notably, the catechol moiety performs two important tasks in parallel; primarily it acts as an efficient anchoring group to metal oxide surfaces, while it furthermore induces the formation of Ag NPs. Attributing to the dual function of catechol moieties, antifouling pSar brush and antimicrobial Ag NPs can not only adhere stably on metal oxide surfaces, but also display passive antifouling and active antimicrobial activity, showing good biocompatibility simultaneously. The developed strategy seems to provide a promising platform for functional modification of biomaterials surface to preserve their performance while reducing the risk of bacterial infections.