PbS/PbI2 nanocomposites were prepared by choosing K[PbI3] as both a lead salt and an iodide precursor and acetone/water as a reaction medium. It was found that the amount of the PbI2 component could be controlled, to some extent, by varying the amount of water used. Further, this simple bicomponent precursor-based synthetic route can be extended to prepare other lead-containing nanocomposites such as Pb3O4/PbI2 and PbSe/PbI2. Because of the heavy-atom effect, PbS/PbI2 nanocomposites exhibited good and composition-dependent electrogenerated chemiluminescence (ECL) performance, demonstrating their potential in the development of novel ECL sensors for analytical and clinical applications. These interesting findings would encourage us to gain deep insight on these phenomena, which could lead to the further development of these new inorganic materials and their applications.