Bioremediation is an efficient process to remove metals and dyes from solutions using different micro-organisms. In the present study, the efficiency of growing Aspergillus flavus (isolated from the effluent of an electroplating industry) to treat a synthetic solution of acid black 52 dye (a trivalent chromium complex dye) was investigated. Maximum removal of dye and chromium was observed to be 390 and 17.22 mg/L, respectively, at an initial dye concentration of 750 mg/L and at pH 4.5 in 50 hours in a batch bioreactor. The biomass concentration was reduced from 4.1 to 0.4 g/L with increasing dye concentration from 100 to 2,000 mg/L. The response surface modeling for color removal was performed using the range of initial dye concentration 200–400 mg/L, pH 4–6 and time 35–50 hours. The optimum conditions for maximum color removal (76.52%) were observed at initial dye concentration: 200 mg/L, pH: 4.75 and time: 50 hours. The deviation (−0.02%) showed a close agreement between the experimental and predicted values of color removal. The scanning electron microscopic and energy dispersive X-ray analyses indicated bioremediation of the dye.