AbstractA colloidal silver oxide hydrosol was prepared for surface‐enhanced Raman scattering (SERS). Its performance as a SERS‐active substrate was tested using benzoic acid and 1,1′‐diethyl‐2,2′cyanine iodide as analytes. SERS and surface enhanced resonance Raman scattering were observed for the adsorbed samples. In the preparation of the sol, the relative amounts of reagents should be an important factor in affecting the surface enhancement of the substrate. The surface enhancement activity of the colloidal hydrosol might indicate that silver oxide films generated in the electrochemical oxidation of a silver electrode could enhance the Raman spectra of adsorbed molecules and/or passivated films.