Nanocrystalline CuIn₃Se₅ thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200 °C for 30 min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional and morphological properties. The XRD patterns reveal the nanoparticles size to be of 18–20 nm diameter, while from the SEM images the nanoparticles size is estimated to be 20–30 nm. It is observed that the annealed films contain nanocrystallites connected with each other through grain boundaries, with grain size of about 100–125 nm and have an overall n-type electrical conductivity and higher photoconductivity. The current–voltage (I–V) characteristics (in dark and light) of these films indicated the formation of a Schottky like junction between the n-CuIn₃Se₅ (OVC) and CdS/ITO layers.