Tin disulfide (SnS2) is attracting significant interest due to the abundance of its elements and its excellent optoelectronic properties in part related to its layered structure. In this work, we detail the preparation of ultrathin SnS2 nanoplates (NPLs) through a hot-injection solution process. Subsequently, Pt was grown on their surface via an in-situ reduction process. The photoelectrochemical (PEC) performance of such nanoheterostructures toward water splitting was subsequently tested. Optimized SnS2-Pt photoanodes provided significantly higher photocurrent densities than bare SnS2 and SnS2-based photocatalysts previously reported. We attribute the excellent activity of the SnS2-Pt photoanodes here reported to a combination of the very thin SnS2 NPLs and the proper electronic contact between Pt NPs and SnS2. Photoelectrochemical impedance spectroscopy was further used to analyze in more detail the effect of Pt on the PEC performance.