Developing effective and simple one-pot synthetic strategies regarding the formation of heterojunction photocatalytic semiconductors remains an intense challenge in research pursuits. Further scheming of the p-n heterojunction has sustained renewed interest in catalysis, photocatalysis, energy storage, and conversion because they easily accelerate the bulk charge separation efficiency. Thus we have successfully designed a Au-MoS2/ZnIn2S4 heterojunction photocatalyst for the first time by adopting a simple one-pot hydrothermal technique, followed by a deposition-precipitation method. By adjusting the mole ratio of Mo with that of Zn and In precursors, we have fabricated a MoS2/ZnIn2S4 p-n heterojunction photocatalyst, and the established p-n heterojunction between MoS2 and ZnIn2S4 is demonstrated by various physicochemical and morphological characterizations. An interfacial junction is created between MoS2 and ZnIn2S4 at the depletion region via an in situ formation mechanism, leading to the enhancement of the charge separation through the p-n heterojunction and thus improving the photocatalytic activity. Moreover, the photocatalytic activity is projected to further improve by the incorporation of Au nanodots on the surface of MoS2/ZnIn2S4 photocatalysts. The increase in activity is due to the generation and participation of a large number of direct-electron-transfer-induced hot electrons in the photochemical reaction. From the experimental results, Au-MoS2/ZnIn2S4 heterojunction photocatalysts with only 1% MoS2 and 1% Au loading content displayed a 561.25 mu mol/h H-2 evolution rate and 84% degradation of phenol, which are nearly 15 and 6 times higher than those neat ZnIn2S4. In addition Au-MoS2/ZnIn2S4 photocatalysts exhibit a photocurrent density of similar to 2.56 mAcm(-2), which is nearly 2.4 times higher than that of the MoS2/ZnIn2S4 heterojunction photocatalyst. This exertion represents the synergetic enhancement of photocatalytic activity through the p-n heterojunction as well as the hot-electron participation by the metal nanocatalyst, which is an inspiration for developing efficient photocatalysts.