The ultrasound (US) assisted one pot method has used to synthesize CuO nanoparticles. The fourier transform infrared spectroscopy (FTIR) spectrum shows a characteristic peak of metal-oxygen bond at 535 cm(-1), which confirms the CuO formation. The high resolution transmission electron microscope (HRTEM) images of the synthesized nano-CuO confirms the size of nanorods with the length of approximately 25-30 nm, and its breadth is less than one nanometer. X-ray diffraction (XRD) pattern of CuO can be readily assigned to those of crystalline CuO, indicating the formation of single-phase CuO with monoclinic structure. The synthesized nano-CuO is mixed with poly(vinyl alcohol) (PVA) to prepare the PVA/CuO nanocomposite to improve the thermal stability of PVA. Their physico-chemical properties are examined by means of FTIR, XRD, differential scanning calorimetry, thermogravimetric analysis, HRTEM, and scanning electron microscope (SEM) techniques.