Dye decolorization of RB19 using commercial laccase (Cerrena unicolor) enzyme was evaluated in this study. The effect of pH, laccase concentration, temperature, metal salt, carbon and nitrogen sources and solvents on the removal of RB19 dye were examined in detail. Highest RB19 removal with laccase (Cerrena unicolor) was obtained at pH 6, 40°C, 0.3 g/L enzyme concentration and 200 mg/L initial dye concentration. According to the Michaelis–Menten kinetics, the highest Vmax was 6.61 mg/L.min at these conditions. 0.25 mM of Cu2+ or Mn2+ enhanced the decolorization of RB19 but further increase in metal concentration decreased the removal of RB19. In the presence of carbon source such as glucose, starch and lactose, removal of RB19 by laccase was not significantly affected. However, in the presence of nitrogen sources such as urea and NH4Cl, the removal of RB19 by laccase was significantly reduced.