Semiconductor quantum dots (QDs) have shown excellent advantages in photocatalysis owing to the unique optical properties, adjustable bandgap, and high specific surface area. However, the small size of QDs also brought severe charge recombination and particle agglomeration issues. Here, a simple QD-mediated precipitation method was used to create 0D/2D nanocomposites of Zn-AgIn5S8 QDs anchored onto NiS nanosheets. The ultrathin Zn-AgIn5S8/NiS nanocomposites show obvious photocatalytic hydrogen production capacity due to the abundant active sites and efficient charge transportation in NiS nanosheets. With 7% of NiS, the maximized H-2 evolution rate reached 5.2 mmol g(-1) h(-1), 11 times that of pure QDs. The apparent quantum efficiency of H-2 production achieves 14.9% at 420 nm at 5 degrees C. Interestingly, the maximum activity was achieved with 7% of NiS, higher than the normally used cocatalysts of 1-3%, which may be attributed to the ultrathin nature of the NiS nanosheets that simultaneously promoted the charge separation and catalytic activity but with minimized light-shielding effect. A reasonable mechanism of 0D/2D nanocomposite photocatalyst was proposed. This study supplies a simple QD-mediated precipitation method for the construction of ultrathin 0D/2D nanocomposites and also a novel strategy to improve the efficiency of sulfide photocatalysts.