A facile sonoemulsion route using suitable non-ionic surfactant, polyethylene glycol with molecular weight of 8000 (PEG8000) was developed to synthesize long CuO nanorods with average diameter of 15–20 nm and lengths up to 1.5 μm. The as-developed CuO nanorods were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, SAED and Raman spectroscopy. The Raman spectrum of as-synthesized nanorods was found to be red-shifted and broadened due to possible consequence of phonon confinement, electron–LO–phonon-coupling and internal compressive stresses. The dynamics of nanorod growth was elaborated in context of size aggregation effect fueled by ultra-sonication and steric hindrance effect imposed by PEG8000. The catalytic activity of CuO nanorods in thermal decomposition of potassium perchlorate was examined by thermogravimetric analysis technique. The CuO nanorods prepared by sonoemulsion route was found to be very effective in thermal decomposition of potassium perchlorate with significant reduction in thermal decomposition temperature.