Nanomaterial shapes can have profound effects on material properties, and therefore offer an efficient way to improve the performances of designed materials and devices. The rational fabrication of multidimensional architectures such as one dimensional (1D)–two dimensional (2D) hybrid nanomaterials can integrate the merits of individual components and provide enhanced functionality. However, it is still very challenging to fabricate 1D/2D architectures because of the different growth mechanisms of the nanostructures. Here, we present a new solvent-mediated, surface reaction-driven growth route for synthesis of CdS nanowire (NW)/CdIn₂S₄ nanosheet (NS) 1D/2D architectures. The as-obtained CdS NW/CdIn₂S₄ NS structures exhibit much higher visible-light-responsive photocatalytic activities for water splitting than the individual components. The CdS NW/CdIn₂S₄ NS heterostructure was further fabricated into photoelectrodes, which achieved a considerable photocurrent density of 2.85 mA·cm^-2 at 0 V vs. the reversible hydrogen electrode (RHE) without use of any co-catalysts. This represents one of the best results from a CdS-based photoelectrochemical (PEC) cell. Both the multidimensional nature and type Ⅱ band alignment of the 1D/2D CdS/CdIn₂S₄ heterostructure contribute to the enhanced photocatalytic and photoelectrochemical activity. The present work not only provides a new strategy for designing multidimensional 1D/2D heterostructures, but also documents the development of highly efficient energy conversion catalysts.