The histamine (His) copper(II) chloride complex Cu(His)Cl2 was synthesized. Its octahedral geometry was confirmed by spectroscopic and X-rays methods. The catalytic activities of the Cu(His)Cl2 complex and the in situ generated copper(II) complexes were evaluated in the oxidation of catechol to o-quinone under atmospheric oxygen. The oxidation rates depend on the nature of the ion salts. A kinetic study revealed that the Cu(His)Cl2 complex has the highest oxidation rate compared to the in situ-formed one.