Nanostructured CuO films have been grown on to the glass substrate by varying the deposition time from 10 to 30 min and substrate temperature from 300 to 400 degrees C by a simple ultrasonic spray pyrolysis technique, using aqueous a cupric nitrate solution as precursor. The effect of the substrate temperature on the textural, structural, electrical, and gas sensing properties of CuO films was studied and correlated. Thermal analysis of the dried precursor shows the elimination of physisorbed and chemisorbed water. It suggests the formation of CuO phase on substrate at temperature of 300 degrees C. X-ray diffractograms of the films indicate the formation of polycrystalline monoclinic CuO having monoclinic with crystallite size around 18 nm. The texture coefficient finds the (0 0 2) plane as the preferred orientation in films. The microstrain and dislocation densities have been calculated and found to decreases with increase in substrate temperature. The scanning electron micrographs indicate the formation of trapezium like facet structures on the film surface. AFM analysis shows uniform deposition of the CuO film over the entire substrate surface. Observations reveal that the film deposited at 300 degrees C show comparatively higher activation energy and appreciable response to ammonia at room temperature. The use of aqueous cupric nitrate as precursor results in the deposition of single phase copper oxide films. Crown Copyright (C) 2011 Published by Elsevier B. V. All rights reserved.