Biosorption is becoming a promising alternative to replace or supplement the present dye removal processes from dye wastewater. In this study, removal of a dye, Basic Blue 9, from an aqueous solution by biosorption on the dead fungal biomass Aspergillus niger was studied. The effective pretreatment method for increasing the biosorption capacity of A. niger was investigated. Autoclaving was found to effectively enhance the biosorption capacity of A. niger to 18.54 mg/g compared with 1.17 mg/g of living cells for Basic Blue 9. Batch pH, kinetic and isotherm studies were conducted to evaluate the biosorption capacity of the pretreated (dead) biomass. The initial pH of the dye solution strongly affected the biosorption capacity and rate. The effective initial pH was between 4 and 6. The equilibrium time varied with the initial pH of the dye solution and was set at 30 h because no significant dye removals occurred after that time of contact. The Lagergren and Ho et al. models can be used to describe the kinetics of Basic Blue 9 biosorption on A. niger successfully for different initial pH values, except for pH 4. At initial pH 4, biosorption of Basic Blue 9 fitted the Langmuir equation well; at initial pH 10, the Langmuir and Freundlich isotherm models both fitted biosorption well. The results of this study indicated that fungal biomass of A. niger can be used for removing Basic Blue 9 from an aqueous solution.