An electrochemical route to synthesize CuO thin films with nano-whiskers like structure, from a metallic Cu precursor is reported. Structural characterization showed the formation of cubic phase for both the Cu and CuO films, whereas, the grains were found to change their shapes from cubic to nano-whiskers as an effect of annealing (in air at 600°C for 30min). X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis, Photoluminescence (PL) and Raman analyses were carried out with the films. The photocatalytic activity of the prepared CuO films was determined by measuring the degradation of Rose Bengal (RB) dye, to find out its potential application in waste water treatment.