The proposed study shows for the first time that gaseous ammonia treatment of AgNO3 and Ce(NO3)3 salts mixture aqueous solution surface gives rise to formation of a composite layer consisting of Ag(0) faceted colloidal crystals and nanoribbons, as well as CeO2 nanocrystals. A study of such a composite carried out by FESEM, XRD, EDX, TEM, STEM and HRTEM methods has shown that the nanoribbons are about 50–150 nm wide and up to 2–3 m long, and that there are 2–3 nm CeO2 nanocrystals on the surface thereof. Colloidal crystals of about several micrometers consist of separate, almost identical silver nanocrystals about 20 nm in size. The obtained results provided a basis for construction of schemes of chemical reactions taking place during the synthesis, and gave grounds for recommendations on practical application of the obtained compounds.