Optical investigation on blue shift behavior of zinc doped cadmium sulphide nano-crystalline thin films have been prepared by spray pyrolysis method at 375 +/- 10 degrees C. The crystallinity and phase have been characterized by glancing angle X-ray diffraction. The XRD peaks confirm the hexagonal structure of cadmium sulphide. The crystallites sizes are found its range of 15-20 nm. The surface morphology is analyzed by using field emission scanning electron microscopy. The morphology of the film is seen as uniform distribution of homogeneous fine solid grains which are compact in nature. Optical absorption spectrum reveals an absorption peak at 475 nm. Indicating that blue shift due to quantum confinement effect, as a result the direct energy gap is increased and found its value is 2.91 eV. Raman spectrum reveals the longitudinal optical phonon peaks are at 302 cm(-1) and 603 cm(-1). The noticeable asymmetry and frequency shift confirm the decrease in particle size. X-ray photoelectron spectroscopy reveals the surface composition and binding energy of elements and it confirm the presence of zinc. The photoluminescence spectrum reveals an emission peak at 728 nm is analyzed. Zn doped cadmium sulphide thin film is useful for window material in solar cells and luminescent red phosphor. (C) 2016 Elsevier B.V. All rights reserved.