Iridium (Ir)-based nanomaterials are promising electrocatalysts for water splitting, and to alleviate their costs as well as improve the performances are always important tasks. Polyoxometalates (POMs) composed of abundant metal, oxygen, and heteroatoms are nanoclusters with defined structures. Benefitting from the inherent advantages of POMs, highly dispersive and “unprotected” Ir nanoparticles originating from Ir-based colloid solution were successfully anchored on POM-derived WO₃/rGO nanocomposites for the first time. Interestingly, the obtained hybrid material Ir/WO_x/rGO delivered improved electrocatalytic performance for water splitting, which is attributed to the addition of only quite small amount of POM derivatives. This work is also the first proof that POM can be employed as precursor to construct metal oxides to support Ir catalysts, providing a new vision for the design of advanced multi-metal electrocatalysts.