A sonochemical approach to the preparation of elongated copper nanoparticles coated with a zwitterionic surfactant, cetyltrimethylammonium p-toluene sulfonate (CTAPTS) is reported. A shape transition of the copper nanoparticles is found to occur due to the presence of an organized medium, consisting of a cylindrical, interconnected network of threadlike micelles. Transmission electron micrographs (TEM) show the presence of elongated copper nanoparticles coated with the surfactant. UV-visible spectroscopic studies point to the elongation of the copper nanoparticles and to the adsorption of the CTAPTS on the surface of the copper nanoparticles, which is corroborated by IR and NMR spectral studies. A monolayer coating of the surfactant is formed on the surface of the elongated copper nanoparticles. This is confirmed by comparing the weight loss obtained in thermogravimetric analysis with that obtained theoretically.