A kinetic study of a hydrogen-transfer reaction from (+)-catechin to galvinoxyl radical has been performed using UV-vis spectroscopy in the presence of magnesium perchlorate in deaerated acetonitrile. The rate constants of hydrogen transfer from (+)-catechin to galvinoxyl radical determined from the decay of the absorbance at 428 nm due to galvinoxyl radical in the reaction of (+)-catechin with galvinoxyl radical increases significantly with an increase in the concentration of Mg2+. The kinetics of hydrogen transfer from (+)-catechin to cumylperoxyl radical has also been examined in propionitrile at low temperature with use of ESR. The decay rate of cumylperoxyl radical in the presence of (+)-catechin was also accelerated by the presence of scandium triflate. These results indicate that the hydrogen-transfer reaction of (+)-catechin proceeds via electron transfer from (+)-catechin to oxyl radicals followed by proton transfer rather than via a one-step hydrogen atom transfer. The coordination of metal ions to the one-electron reduced anions may stabilize the product, resulting in the acceleration of electron transfer.