The oxidative decolorization of Brilliant Blue FCF (BBF) in aqueous solution was studied using a Fentonlike (H2O2/Fe3+) reaction in a dark environment. The effects of operational parameters, such as H2O2, Fe3+, and initial dye concentrations, were investigated. Results indicated that by increasing the initial concentration of H2O2 and Fe3+ the rate of BBF decolorization was enhanced; however, the rate of BBF decolorization decreased with an increase in the initial concentration of BBF. In addition, the influence of aromatic additives and Orange II on the efficiency of BBF removal was examined. The decolorization rate of BBF in the presence of various aromatic additives obeyed the following order: gallic acid > hydroquinone > salicylic acid > 2-nitrophenol > 1,4-dihydroxynaphthalene. The rate of BBF decolorization increased as the initial concentration of hydroquinone additive increased up to 5 × 10-5 M, but beyond this there was a decrease in the decolorization rate. Mineralization of the dye solution was determined by measuring the reduction of chemical oxygen demand (COD). For a dye solution with a COD of approximately 45 ppm and dye concentrations less than 5 × 10-5 M, complete color removal and 80% mineralization was obtained after a reaction time of 150 min under optimized conditions. © TÜBİTAK.