Polycrystalline cadmium hydroxide nanomaterials have successfully been synthesized by composite-hydroxide-mediated approach with growth time variation. The influence of growth time on structural, morphological, elemental, and optical properties was explored using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and ultraviolet–visible spectroscopy. X-ray diffraction results revealed the hexagonal and monoclinic phases of cadmium hydroxide along with rhombohedral impurity phase of cadmium carbonate. Fourier transform infrared spectroscopy further endorsed the X-ray diffraction results and confirmed the Cd–O bonding vibrations. Time-dependent uniform distribution of spherical morphology was observed in the scanning electron micrographs of the product. The presence of cadmium and oxygen in the energy dispersive X-ray spectroscopy results fingerprinted the purity and formation of the desired nanomaterials. Crystallite size was decreased with the increase of growth time as estimated by the Debye–Scherrer method. Furthermore, the optical bandgap was measured by Tauc’s relation using ultraviolet–visible absorption spectra and found to be in the range of 3.2–3.5 eV.