We are studying the chemically modified laccase from Trametes versicolor for use in the in vitro oxidation of two polycyclic aromatic hydrocarbons (PAHs), acenaphthylene and anthracene, in combination with 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a redox mediator. The results indicate that the maleic anhydride modified laccase (MA-Lac) improved the stability of laccase to temperature, pH and storage time compared with the free enzyme. After incubation for 72 h, the MA-Lac–ABTS system oxidized acenaphthylene and anthracene to more than 70% from the reaction mixture.