ABSTRACT Dye stuff released to the ecosystem from textile industries cause a serious contamination and become a major environmental problem over the last few decades. As biological decolorization of textile wastewater is an important issue, Fusarium . acuminatum was used to removal of a frequently used textile dye, methyl orange. Live pellet of Fusarium acuminatum was used and decolorization studies performed in various temperatures and pH conditions with different dye concentrations. The highest decolorization rate was observed at 35ᴼC. 60 mg/L was found as the optimum initial dye concentration. In the pH range of 3-4, decolorization rate was approximately 70%. It was seen that Fusarium acuminatum have the great ability of the methyl orange removal. To our knowledge, it took place for the first time in the literature.