Electrochemical impedance spectroscopy and cyclic voltammetry techniques were employed to study borohydride oxidation on a polycrystalline Pt electrode in an aqueous alkaline media containing 0.05 M NaBH4 and 1 M NaOH. Determined current density changes were interpreted in combination with EIS measurements. The regions of decreasing anodic current leading to negative polarization resistance, R-p, were supposed to be appreciably related to increasing availability of oxygen-containing species (OHad and Pt oxides) on the Pt surface in the presence of the accumulated borohydride species. Possible borohydride oxidation processes and electrical circuits were discussed regarding the potential applied.