This study demonstrates high-performance visible-light-driven H 2 -evolution photocatalysts based on novel CdS nanodiamonds. The CdS nanodiamonds (~100 nm) were prepared by optimizing the molar ratios of Cd to S (Cd/S = 1:8) via a hydrothermal method. Various amounts of MoS 2 nanosheets were decorated on the surface of the CdS nanodiamonds. The 6 wt% MoS 2 /CdS nanocomposites exhibited the highest H 2 evolution rate (32.94 mmol g −1 h −1 ), which was 3 times (10.37 mmol g −1 h −1 ) higher than that of the pristine CdS nanodiamonds under visible light irradiation. The underlying reasons for the enhanced photocatalytic performances were investigated by measuring the electro-chemical properties of the composites, suggesting that the improved performances were attributed to suitable optical adsorption range, low recombination rate of the photo-generated electrons and holes, extra generated charges, excellent charge transfer ability, and increased donor density. This study offers new insights for preparing the CdS nanoparticles with novel structures and high-photocatalytic performances for solar‑hydrogen energy conversion. • Diamond-like CdS particles were prepared and optimized by adjusting the molar ratios of Cd to S. • MoS 2 nanosheets were used to decorate the optimized CdS nanodiamonds. • Decorating MoS 2 nanosheets enables to effectively enhance photocatalytic performance and reduce photo-corrosion. • The enhanced performance results from extra photogenerated charge carries, improved charge separation and transfer ability.