Cadmium ion is toxic to organisms and shows persistence because of its nondegradability. Photoreduction of the cadmium ion (Cd­(II)) was studied using a bentonite-supported Zn oxide (ZnO/BT) photocatalyst in an aqueous medium under ultraviolet light. The prepared ZnO/BT photocatalyst was characterized by diffuse reflectance spectroscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, and Brunauer–Emmett–Teller/Barrett–Joyner–Halenda analysis. The effects of main parameters including pH, contact time, initial concentration of cadmium­(II) ion, light intensity, temperature, and the photocatalyst dosage were investigated for obtaining appreciate reduction/removal efficiency. The maximum reduction/removal efficiency of 74.8% was obtained at optimized values which were found to be at pH 5, 6 h contact time, 6 ppm Cd­(II) ion, 200 W UV light, 45 °C temperature, and 4 g/L of ZnO/BT. Reduction/removal of Cd­(II) was significantly affected by light intensity so that the increment in UV intensity from 0 to 200 increased the reduction/removal efficiency from 61.2 to 76.8%. This study reports an inexpensive and environmentally friendly photocatalyst for Cd2+ reduction in real samples and prospective photoelectric materials.