Development of biomaterials with long-term biocompatibility, durability, and stability remains a critical challenge for biomedical devices. Here, we synthesize, characterize, and graft poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA) onto both gold surfaces and gold nanoparticles (AuNPs) via surface-initiated atom transfer radical polymerization (SI-ATRP) to form a stable antifouling coating to resist nonspecific protein adsorption and bacterial attachment. Surface plasmon resonance (SPR) results demonstrate that all of polyHEAA brushes coated on the gold substrate at a wide range of film thickness of similar to 10-40 nm can achieve almost zero protein adsorption from undiluted blood plasma and serum for 1 h, while static bacteria assay results show that polyHEAA brushes prohibit long-term bacterial colonization by Staphylococcus epidermidis and Escherichia coli RP437 up to 3 days. Moreover, the polyHEAA-coated AuNPs with different diameters remain their hydrodynamic sizes unchanged in human blood plasma and serum for up to 7 days. All these data indicate that polyHEAA can serve as promising biomaterials with long-term biocompatibility and durability suitable for applications in complex biological media.