Finely dispersed sandwich composite nanoparticles of Cu–Ni–Cu were prepared by a novel method combining template synthesis and an ultrasonic treatment method. The composite nanoparticles have uniform cylinder shape with tunable diameter and length. Transmission electron microscopy (TEM) and electron diffraction (ED) were employed to characterize the nanoparticles. This method can be used to fabricate shape- and size-controlled composite nanoparticles in a wide range of metals and other materials. The so-prepared particles may be suitable candidates as nanoscale blocks for assembling nanodevices.