Decolorization of reactive brilliant blue KN-R by Aspergillus ficuum was investigated on suspended spores, mycelial pellets, immobilized cells. It was found that Aspergillus ficuum could effectively decolorize reactive brilliant blue KN-R especially when grown as pelleted mycelia. Many factors affecting the decolorization process in nitrogen-limited media (NLM) were studied, including: initial pH, temperature, and mycelial age. Results showed that the media containing reactive brilliant blue KN-R at 50 mg/L could be decolorized by 96% of the initial color in 42 h, in most conditions tested, the dye degraded products assayed by UV-visible spectrophotometer and macroscopic observation showed that the decolorization of reactive brilliant blue KN-R by mycelial pellets includes two important processes: biodegradation and biosorption. Kinetic study revealed that reactive brilliant KN-R biodegradation by mycelial pellets and suspended spores conformed to first-order reaction model while reactive brilliant blue KN-R biodegradation by immobilized cell followed zero-order model. In addition, mycelial pellets was found to biodegrade KN-R more quickly than suspended spores and immobilized cell.