In this study, metal-polymer particles with microphase-separated structures were prepared by self-organized precipitation, where a good solvent is evaporated from a solution that also contains block copolymer, Au NPs, and a poor solvent. Control of the microphase-separated structure in composite particles consisting of Au NPs and block copolymer was accomplished by changing the Au NP size, the mix ratio, and the copolymerization ratio of the block copolymer. The morphology of the inner structures was changed from a lamellar phase to a spherical phase by increasing the Au NP concentration. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1717-1722, 2011