In this work, a facile and carbon-mediated hydrothermal route has been developed for fabrication of core–shell structured SnO₂@TiO₂ nanocomposites with excellent photocatalytic performance for the degradation of the organic dye rhodamine B (RhB). The heterostructures were formed by using SnO₂–C nanospheres as the core and TiO₂ as the outer shell, followed by calcination. The as-synthesized SnO₂@TiO₂ products have uniformly spherical morphology with an average diameter of 64 nm and the thickness of TiO₂ shell was about 4 nm. Additionally, the structure and properties of the products were greatly affected by the calcination temperatures and the carbon content. In comparison to the SnO₂@TiO₂ synthesized in the absence of carbon, the SnO₂@TiO₂ composite exhibited a better photocatalytic performance for the decomposition of RhB. In particular, the carbon-mediated SnO₂@TiO₂-550 product showed superior properties including a large specific surface area for supplying abundant active sites and unique heterojunctions for helping to facilitate the charge separation. As a result, the photocatalytic performance was notably enhanced owing to the above synergistic effect. We expect that the present method based on a carbon-mediated process may be used for the preparation of other nanocomposites.