This study reports the effective fabrication of monodisperse and spherical silver nanoparticles by vacuum evaporation on running hydrocarbon solution in a cylindrical glass chamber. In this synthesis, a nonionic surfactant, sorbitan monooleate, was added to the reaction medium as the protective agent for the nanoparticles, and the effect of its concentration on the particle size was investigated in detail using transmission electron microscopy and UV-vis spectroscopy.