Uniformly dispersed copper oxide nanoparticles in poly(vinyl alcohol) (CuO-PVA) have been synthesized by the sonochemical method. The properties of the as-prepared composite material are characterized by XRD, DSC, thermogravimetric analysis (TGA), TEM, and diffuse reflection spectroscopy (DRS). A band gap of 2.1 eV is estimated from DRS measurements. The controlled crystal growth of copper oxide has been studied by using the as-prepared CuO-PVA composite as seed for the crystal growth of copper oxide. Well-shaped crystals of 1 mum in length were grown.