We prepared multicomponent composites of layered hexaniobate, a photocatalytically active layered semiconductor, with cationic organic species of methylviologen as an electron acceptor, proflavine as a photosensitizing dye, and triethanolammonium as a sacrificial donor. Two types of composites with different location of methylviologen, which was incorporated in the interlayer spaces or adsorbed on the external surfaces, were obtained. Visible light irradiation caused photoreduction of methylviologen in the composites, which was ascribed to the photoinduced electron transfer initiated by the photoexcitation of the proflavine dye. The location of methylviologen affected aggregation of the photoreduced methylviologen. A mixture of the three organic species without the niobate did not cause the reduction of viologen but self-decomposition of the proflavine dye under the same irradiation conditions, which indicated that the semiconducting niobate layers were indispensible for transferring electrons from the photoexcited dye to the acceptor.