In this work, copper oxide films were deposited at different substrate temperatures of 200, 250, 300 and 350+/-5 degrees C by ultrasonic spray pyrolysis technique and the effect of substrate temperature on the structural, surface, optical and electrical properties of the films was presented. The film structures were studied by X-ray diffraction (XRD). To obtain information about structural properties in detail, the grain size (D), dislocation density (delta) and lattice parameters (a = b = c for cubic structure) for preferential orientations were calculated. The surface properties and elemental analyses were characterised using scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Optical properties of the films were analyzed by transmission, linear absorption coefficient and reflection spectra, and the optical method was used to determine the band gaps of the films. The current-voltage values were measured with two-probe technique, and the electrical conductivities were calculated. Consequently, it was determined that substrate temperature has a strong effect on the structural, surface, optical and electrical properties of copper oxide films. (C) 2008 Elsevier B.V. All rights reserved.