Being an optical semiconductor, tin disulfide (SnS2) attracts increasing interest in the fields of heterogeneous photocatalysis and photovoltaics. However, support from a graphene sheet in the form of a nanocomposite is expected to increase the stability and effectiveness of a SnS2 material in potential applications. We report here novel nanocomposites of graphene-oxide-stacked hexagonal-shaped pristine SnS2 nanodiscs (NDs of two different sizes) and nanosheets synthesized using an in situ one-pot hydrothermal synthesis process and the application of the nanocomposite as an efficient heterogeneous photocatalyst. The as-synthesized morphology-oriented nanoparticles and nanocomposites were comprehensively characterized, and finally, excellent photocatalytic activity of reduced graphene oxide/SnS2 nanocomposites under visible-light irradiation was analyzed using UV-vis spectroscopy, high-performance liquid chromatography, and gas chromatography. While precisely manipulating the nanocomposite formation, we observed efficient visible-light-driven photocatalytic application of graphene-stacked SnS2 NDs in the quantitative synthesis of aniline (99.9% yield, absolute selectivity) from nitrobenzene (>99.9% conversion), in the reduction of toxic Cr(VI) to nontoxic Cr(III), and in the degradation of mutagenic organic dyes. A possible synergetic electrical and chemical coupling leads to effective carrier separation in the semiconductor and charge transport in the nanocomposite, which finally gives rise to efficient tandem photocatalysis reactions.