Fine palladium (Pd) particles, which have a diameter of 4-5 nm and are coordinated with the poly(2-vinylpyridine) homopolymer (P2VP) or poly(2-vinylpyridine)-block-polyisoprene diblock copolymer (P2VP-b-PI). were prepared by the reduction of palladium acetylacetonate (Pd-II(acac)(2)) with 1-propanol in the dilute benzene solution of P2VP or PBVP-b-PI. These Pd "nanoparticles" were selectively incorporated into a particular region of microdomains by casting a solution comprised of the Pd nanoparticles, PBVP-b-PI, and chloroform as a solvent into film specimens. The nanoparticles coordinated with P2VP were selectively incorporated into the P2VP domains, while those coordinated with PBVP-b-PI were around the interface between the P2VP and PI domains.