TiO₂/(ZnS)_x(CuInS₂)_1−x nanocomposites were prepared from oleic acid-capped TiO₂ nanocrystals and alloyed (ZnS)_x(CuInS₂)_1−x nanocrystals. Element mapping and transmission electron microscopy (TEM) results suggested that the nanocomposites exhibit homogeneous composition with uniform mesoporous structure. High photocatalytic activities driven by simulated solar light were achieved owning to their high surface area and efficient electron transfer from (ZnS)_x(CuInS₂)_1−x to TiO₂. This work enables the synthesis of a large variety of photocatalysts from nanocrystal building blocks for various applications beyond photodegradation of organic pollutants.