Cadmium selenide nanostructured films were prepared using the high-frequency (HF) magnetron sputtering method. All samples were deposited on quartz substrates in disk form with a radius of 16 mm. The temperature of the substrate was maintained at 180 °C for all samples. The deposition times were 3, 6, 9, 12 and 20 min. The effect of deposition time on the optical properties of CdSe nanostructured films was investigated by X-ray diffraction (XRD), optical absorption spectra (OAS), a scanning electron microscope (SEM) and an energy-dispersive X-ray analyser (EDX). XRD analysis of the obtained samples exhibited a cubic structure with a preferred (200) orientation. The average crystallite size of the CdSe nanostructured films was determined using the Scherrer equation. An increase in deposition time was found to result in a corresponding increase in crystallite size. The EDX showed that the CdSe nanostructured films were formed from the desired elements, and their distribution was uniform. SEM analysis showed that the surface morphologies of the CdSe nanostructured films were dependent on the deposition time. OAS was analysed using the Tauc model. The absorption spectrum fitting (ASF) method was applied to estimate the optical band gap and Urbach energy of the CdSe nanostructured films. The optical band gap and Urbach energy were found to decrease with increasing deposition time. This behavior is ascribed to the growth in particle size.