CdS is a popular photocatalyst and has gained widespread attention for use in photocatalytic systems that harness solar energy for chemical transformations. However, the fast recombination of photogenerated electron− hole pairs in CdS restricts its practical applicability. Because MoS 2 facilitates charge separation and boosts photocatalytic activity, it has been integrated with CdS to overcome this difficulty. In this study, CdS/MoS 2 heterostructured nanocomposites were successfully synthesized via a one-step solvothermal method with control of the MoS 2 content. The enhanced photocatalytic performance of MoS 2 /CdS nanocomposites for the selective oxidation of 5hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) was investigated under anaerobic conditions with visible light irradiation. The optimal MoS 2 content was determined to be 4.5%, which results in complete HMF conversion with nearly 100% selectivity toward DFF within 2 h of irradiation. In situ XPS analysis confirmed that upon photoexcitation of MoS 2 /CdS, photogenerated electrons were rapidly transferred from CdS to MoS 2 , leading to hole accumulation in CdS and electron accumulation in MoS 2 and therefore facilitating efficient charge carrier separation. Thus, the MoS 2 /CdS composites exhibited significantly higher photocatalytic activity than pristine CdS, owing to the effective suppression of electron−hole recombination. This work not only deepens the understanding of photocatalytic mechanisms but also underscores the potential of MoS 2 /CdS composites in environmental and energy-related applications. These findings contribute to the advancement of photocatalytic materials science for the development of efficient and sustainable technologies for chemical synthesis and environmental remediation.