This study investigated the degradation of 4-chlorophenol (4-CP) by Caldariomyces fumago chloroperoxidase (CPO). Enzymatic oxidations were studied in reaction mixtures at pH 3.0, 4.0, and 6.0 in the presence and absence of Cl- containing 3.5 IU of CPO and 4-CP and hydrogen peroxide concentrations within the range of 0.5-50 and 0.005-50 mM, respectively. Distinct patterns of products regarding color, concentration, and solubility were observed. Reaction mixtures at pH 6.0 containing 3.5 IU of CPO and 5.0 mM 4-CP and H2O2 (1:1 stoichiometry) showed the highest 4-CP removal of 95% and the highest formation of a dark precipitate.