This article reports on the fabrication and characterization of plasmonic interfaces composed of a sandwiched structure comprising a tin-doped indium oxide (ITO) substrate, gold nanostructures (Au NSs), and a thin ITO film overcoating. The change in the optical characteristics of the ITO/Au NSs/ITO interfaces as a function of the ITO overlayer thickness (d(ITO) = 0-200 nm) was followed by recording UV-vis transmission spectra. The influence of the thickness of the ITO overcoating on the position and shape of the plasmonic signal is discussed. The possibility to functionalize the ITO/Au NSs/ITO interfaces chemically is demonstrated by covalently linking ethynyl ferrocene to azide-terminated ITO/Au NSs/ITO interfaces. The resulting interfaces were characterized using X-ray photoelectron spectroscopy (XPS), electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques, and UV-vis transmission spectroscopy.