The electrochemical/chemical growth of porous (Ni,Co,Cu)(OH)2 was reported based on the corrosion behaviors of Ni-Co-Cu films in neutral salt spray. The films prepared by using electrodeposition were ternary solid solution alloys with a simple phase structure, strong texture, nanoscale grains, large microstrain and a large number of crystal defects. The unique microstructures coupled with extensive ion diffusion during the subsequent corrosion process facilitated the formation of ternary hydroxides with uniform and porous nanostructures. The ternary hydroxides composed of Ni-/Co-dominant hydrotalcite-like and Cu-dominant orthorhombic (Ni,Co,Cu)(OH)2 could be efficiently prepared by motivating the transformation from oxide to hydroxide. The binder-free (Ni,Co,Cu)(OH)2 electrode exhibited a high specific capacitance of 1738 F g−1 at a current density of 20 A g−1 and decent cycling stability. The electrochemical/chemical growth mode, uniform porous nanostructures and nature of the ternary hydroxides could account for the superior electrochemical performances. This work proposed a simple and green approach to prepare multicomponent hydroxides as novel electrode materials for rechargeable batteries and hybrid supercapacitors.