The very high aspect ratio (14) and deep (132 mum) channels of an UV-embossed polymeric microstructured surface were successfully metallized by electroless nickel plating. A submicron conformal and highly adherent nickel coating was uniformly deposited on all the hydrophobic silicone-enriched surfaces of the channels. The nickel surface layer acts as a diffusion barrier and also allows for easy subsequent chemical modification by chemical grafting, electroplating, or electropolymerization for diverse applications in micromolding, microfluidics, sensors, microreactors, biomedical devices, and so forth. Hence, electroless nickel plating combined with UV embossing allows easy fabrication of high aspect ratio metallized polymeric microstructures with tailored surfaces.