A novel approach for preparing hierarchical porous nickel structures has been developed. It is an aqueous processing of the template, macroporous silicon, which was etched in HF solution to have straight channels. By immersion in a prepared nickel solution, the silicon sidewalls were replaced by nickel deposits to form a total metallic structure. Since silicon framework was gradually consumed during the displacement reactions, the deposited nickel displayed additional feature of being highly porous on the sidewalls. With the initial straight microchannels, the metal structure was hierarchically porous.