Coral-like branched architectures comprised of single-crystal copper nanocrystals were synthesized at room temperature through a galvanic displacement reaction between aqueous CuCl₂ and Al foil in the presence of a cationic double-chain surfactant diocta-decyl-dimethyl-ammonium bromide. The corals are monolithic single crystals consisting of nanorod stems with an axis along ⟨001⟩ and orthogonal branches along ⟨110⟩. The branch diameters fall in a narrow range between 80 and 100 nm, and the branch lengths vary between 200 and 800 nm. The branch density is controllable by adjusting the surfactant/metal-ion ratio in solution and reaction time. These branched structures could serve as attractive building blocks for creating interconnected nanorod networks or porous materials for diverse applications, including catalysts, sensors, solid-state refrigerators, and nanodevices.