Developing highly efficient and economical co-catalysts to enhance the photocatalytic H₂ evolution performance has received extensive attention in the last few years. Herein, cauliflower-like Mn_0.2Cd_0.8S (MCS) decorated with ReS₂ nanosheets was hydrothermally fabricated and exhibited an enhanced H₂ evolution activity. The 5 wt% ReS₂/MCS composite obtained an optimal H₂ evolution rate of 17.31 mmol g⁻¹ h⁻¹, which was approximately a 10-fold improvement over that of pure MCS. The coupling of Mn_xCd_1−xS and ReS₂ could form superior interfacial contacts between the two components and offer a feasible route to promote the charge separation efficiency. Moreover, as a co-catalyst, the two-dimensional nanosheet structure of ReS₂ was conducive to exposing more active sites to boost surface H₂ evolution reactions.