The biosorption of five anionic dyes, namely, Brilliant Blue R, Remazol Brilliant Blue R, Reactive Orange 14, Reactive Red 120, and Reactive Black 5 onto dried Aspergillus tubingensis, a newly isolated filamentous fungus, was examined. The most important parameters for the biosorption process, such as dye type, pH (2-10), time (0-240 min), and initial dye concentrations (40-390 mg/l), were optimized. The highest equilibrium uptake was determined as 143.0 mg/g at 390 mg/l Brilliant Blue R concentration at pH 2. The adsorption equilibrium data fit the Langmuir model best in the Brilliant Blue R dye concentration range studied. The pseudo-second-order kinetic model has high efficiency and performance for the interpretation of real data. The application of A. tubingensis biosorbent for the removal of Brilliant Blue R dye from wastewaters can be suitable for the fabrication and designing of wastewater treatment plants by using these equilibrium and kinetic parameters. To the best of our knowledge, this is the first report about the usage of A. tubingensis biomass for low cost synthetic dye removal process.