The decoloration of amaranth, as one of the azo dyes widely used in the dyeing industry, was carried out using a two-compartment cell separated by Pd sheet, palladized Pd (Pd/Pd black) sheet and platinum-modified palladized Pd (Pd/Pd black/Pt) sheet electrodes. The Pd/Pd black/Pt electrode was the most effective one for the decoloration of amaranth. The products of the decoloration reaction were identified by high-performance liquid chromatography (HPLC) and UV-visible (VIS) absorption spectroscopy. The results clearly indicated that the decoloration was caused by the hydrogenolysis of amaranth by means of atomic hydrogen permeating through the electrodes or the severance of the azo group as a result of its hydrogenation. The current efficiency for the decoloration of amaranth reached 97% when its initial concentration was 0.17 M.