High density polyethylene (PE) was modified by argon plasma discharge and then coated with 50 nm thick gold layer. Surface morphology of as-modified PE samples and samples coated with Au was studied using atomic force microscopy technique. The surface polarity was characterized by contact angles measured by standard goniometry. A nanoindenter was used to examine the sample's mechanical properties (hardness, elasticity modulus, scratch behavior). The Au layers were characterized using X-ray diffraction. The plasma modification of PE leads to a strong decrease of the water contact angle, which further depends on the time elapsed after the plasma treatment. Because of plasma-initiated ablation, a lamellar arrangement of PE polymeric chains becomes apparent on the plasma-treated samples. The roughness of as-modified PE decreases as a result of Au deposition. Plasma treatment increases PE microhardness but after subsequent Au deposition, both microhardness and elastic modulus decline. Scratch tests showed that while on Au-coated pristine PE samples mainly elastic deformation was observed, on plasma-treated and subsequently Au-coated samples plastic deformation and mechanical deterioration played a significant role. According to the XRD analysis, Au film deposited on the modified PE should be the most stable.