Ag2S/Ag heteronanostructure has been produced by a simple one-stage chemical deposition from aqueous solutions of silver nitrate, sodium sulfide, and sodium citrate with the use of monochromatic light irradiation. For simultaneous synthesis of Ag2S and Ag nanoparticles, deposition has been performed from reaction mixtures with reduced sodium sulfide concentration. The size of Ag2S and Ag nanoparticles is 45–50 and 15–20 nm, respectively. It is established that in the contact layer between silver sulfide and silver, nonconducting a-Ag2S acanthite transforms into superionic b-Ag2S argentite under the action of external electric field. The scheme of the operation of a resistive switch based on an Ag2S/Ag heteronanostructure is proposed. The UV–Vis optical absorption spectra of colloidal solutions of Ag2S/Ag heteronanostructures have been studied.