We present a spectroelectrochemical fiber-optic sensor with an optically transparent electrode. The sensor was fabricated by coating indium tin oxide (ITO) onto the surface of fiber-optic core chips using a polygonal barrel-sputtering method. The ITO-coated fiber-optic probe can be simply and cheaply mass-produced and used as a disposable probe. The sensing is based on changes in an attenuated total reflection signal accompanying the electrochemical oxidation-reduction of an analyte at the electrode. The properties of an ITO-coated fiber-optic probe as an optically transparent electrode were investigated for varying thicknesses of ITO. The sensor responses were successfully enhanced with an additional level of selectivity via an electrostatically adsorbed, self-assembled monolayer, which comprised a polyanion and polycation.