We propose a novel technique for electroless plating on polymer substrates using a dense CO2 beyond the critical point. Ni-P thin films were fabricated by a novel, hybrid technique consisting of two processes: catalyzation in supercritical CO2 with Pd bis-acetylacetonate and electroless plating in emulsion with dense carbon dioxide. Catalyzation in supercritical CO2 enabled the nucleation of a large number of Pd nuclei on a polyimide substrate without chemical pretreatment, and the deposition of a uniform Ni-P metal film. The electroless plating in emulsion with dense carbon dioxide produced a uniformly plated film without peeling or nodules. The improved uniformity was attained by the solubility and diffusivity of the dense CO2 beyond the critical point in the emulsion.