Three-dimensional (3D) platinum–cobalt alloy networks nanostructures with a high alloying degree were synthesized through a room temperature wet-chemical synthetic method using the K₂PtCl₄/K₃Co(CN)₆ cyanogel as reaction precursor in the absence of surfactants and templates. The size, morphology and surface composition of platinum–cobalt alloy networks nanostructures were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), selected area electron diffraction (SAED), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The 3D backbone structure and double-metallic property of the K₂PtCl₄/K₃Co(CN)₆ cyanogel are responsible for the 3D structure and the high alloying degree of the as-prepared products, respectively. Compared to the pure Pt nanoparticles, 3D platinum–cobalt alloy networks nanostructures exhibit superior electrocatalytic activity and stability for the methanol oxidation reaction (MOR), which is ascribed to their unique 3D structure and alloy properties.