Uniform and well-defined inorganic–organic hybrid nanobelts of the hexagonal wurtzite ZnSe·N₂H₄ having an average width of 200 nm, a mean thickness of 25 nm, and a typical length of a few micrometres have been grown facilely in an aqueous solution, and characterized by measuring photoluminescence spectra and kinetic profiles as well as diffraction patterns and electron microscopic images. The length-to-width and width-to-thickness ratios of ZnSe·N₂H₄ nanobelts have been controlled well by adjusting [Se]-to-[ZnCl₂] ratios as well as reaction time and temperature in hydrazine-hydrate-assisted hydrothermal reactions. A sufficient amount of the selenium precursor has been found to be essential for the one-dimensional growth of crystalline ZnSe·N₂H₄ nanobelts. Photoluminescence from ZnSe·N₂H₄ nanobelts shifts to the red by 16 nm and increases 3.5 times with the increase of the [Se]-to-[ZnCl₂] ratio. The mean lifetime of photoluminescence kinetics having three decay components of 18 ps, 85 ps, and 1300 ps increases with the length-to-width ratios of ZnSe·N₂H₄ nanobelts.