Tin disulfide (SnS2) is attracting significant interest because of the abundance of its elements and its excellent optoelectronic properties in part related to its layered structure. In this work, we specify the preparation of ultrathin SnS2 nanoplates (NPLs) through a hot-injection solution-based process. Subsequently, Pt was grown on their surface via in situ reduction of a Pt salt. The photoelectrochemical (PEC) performance of such nanoheterostructures as photoanode toward water oxidation was tested afterwards. Optimized SnS2-Pt photoanodes provided significantly higher photocurrent densities than bare SnS2 and SnS2-based photoanodes of previously reported study. Mott-Schottky analysis and PEC impedance spectroscopy (PEIS) were used to analyze in more detail the effect of Pt on the PEC performance. From these analyses, we attribute the enhanced activity of SnS2-Pt photoanodes reported here to a combination of the very thin SnS2 NPLs and the proper electronic contact between Pt nanoparticles (NPs) and SnS2.