Discharge of textile dyes in wastewater of textile factories represents a major environment problem threatening the aquatic life. The decolorization of such harmful chemicals is of paramount importance. In this work, Aspergillus niger, a brown rot fungi, isolated from the effluent samples around the textile industry of El- Baragil, Giza, Egypt was evaluated for its efficiency in decolorization of two textile dyes; Remazole blue and Remazol red. Effluent samples were also analyzed for their physiochemical properties. The optimum conditions for decolorization were found to be 4 days incubation, 30 ° C and pH4 in Sabouraud liquid medium supplemented with dextrose (10 g/l) and ammonium sulfate (2 g/l) as a carbon and nitrogen source, respectively. The response of the isolate to the increase in dye concentrations was found to be growth inhibitory. Decolorization extent and facile conditions showed the potential for the A.niger to be used in biological treatment of textile dyes.