Uniform hexagonal Cd(OH)2 nanoplates have been produced directly on Cd substrates by a hydrothermal process in alkaline solution containing (NH4)2S2)8 without the use of templates or surfactants. The Cd foil serves as both the Cd source and substrate. The morphology, structure, and composition of the Cd(OH)2 nanoplates are characterized by X-ray diffraction, electron microscopy, selected area electron diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The Cd(OH)2 nanoplates are single-crystalline and possess a well defined hexagonal shape. The thicknesses of hexagonal Cd(OH)2 nanoplates range from 30 to 80 nm and the lateral lengths are about 80-200 nm. The growth mechanism is also discussed.