Copper doped Cadmium sulfide (CdS) nanostructures were assembled on flexible cellulose acetate substrates using low cost sol–gel route. The effects of doping concentrations of copper (Cu) on the CdS nanostructures were studied. The sol was prepared in ultrasonic environment and used for the growth of films using spin coater. The particles and films were characterized by structural, morphological, elemental, optical and electrical studies. Micrographs obtained by field emission scanning electron microscopy (FESEM) reveal the rod shape formation in the presence of Cu with increasing doping concentrations Williamson Hall plots obtained using x ray diffraction (XRD) studies indicate the presence of stress in the lattice due to copper doping. The reduction in crystallite size is observed from 7.29 nm to 5.66 nm. Current–voltage curves exhibit ohmic behavior with an appreciable increase in the conductivity with increasing Cu doping concentrations. Samples show excellent photoluminescence behavior with good absorption spectra in the visible region.