Organometal trihalide perovskite solar cells (PSCs) have been widely recognized as a promising photovoltaic device due to their impressive set of outstanding excellent optoelectronic properties. However, the instability and intermittent energy output caused by the intensity fluctuation and/or the daily cycle of sunlight have motivated the direct application of PSCs in other energy fields. Here, we report an integrated solar-energy-conversion/water-splitting device comprising a single-junction PSC and CdS-decorated TiO 2 nanorod array (i.e., semiconducting CdS/TiO 2 NRA nanocomposite) photoanode with excellent photoelectrochemical (PEC) performance. Intriguingly, the introduction of PSC is found to effectively suppress the recombination of electrons and holes during the PEC catalytic process. As a result, the integrated device yields an overall solar-to-hydrogen efficiency of 1.54% and exhibits a six-fold increase in the degradation rate of methylene blue over that of the CdS/TiO 2 NRAs alone. As such, the crafting of a perovskite solar cell-assisted nanocomposite semiconductor photoanode may represent a viable route to alleviating the electron-hole recombination in water splitting and the degradation of organic pollutants, thus rendering the effective implementation of PSCs.