Herein, we report engineering of nanostructured p-CuIn3Se5/n-CdS heterojunction thin film on a glass substrate, which is prepared at room temperature using simple wet chemical approach involving ion exchange reactions between CdS and Cu+, In3+ and Se2- ions in alkaline medium. The uniform deposition of heterojunction thin films is achieved by optimizing the pH, temperature and molarity of the reactant bath. The as-deposited thin-films were annealed at 200 degrees C in air for 1 h and further characterized for structural, optical and electrical properties using UV-Vis spectrophotometer, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Hall effect for type of conductivity, and I-V measurement to investigate the charge conduction phenomenon. The characteristic (1 1 2) and (1 1 0) planes in XRD and the electron diffraction pattern could confirm the formation of CuIn3Se5. The chemical composition and the band gap energy E-g =1.4 eV of the nanostructured p-CuIn3Se5/n-CdS heterojunction thin-films were confirmed using XPS and the absorbance spectra, respectively. Based on the data and energy band gap calculations of CuIn3Se5 and CdS thin films, the probable band alignment between the nanostructured p-CuIn3Se5/n-CdS heterojunction is proposed. (C) 2011 Elsevier B.V. All rights reserved.