Biodecolorization of synthetic wastewater containing azo dyes, Direct Red-80 (DR-80) and Mordant Blue-9 (MB-9), both individually and together, using immobilized Phanerochaete chrysosporium in a batch-operated rotating biological contactor (RBC) reactor was investigated. Following initial startup of the RBC reactor, which took almost 1 month, results on dye decolorization and enzyme activities of lignin peroxidase (LiP) and manganese peroxidase (MnP) by the fungus were obtained. From experiments involving the individual dyes, decolorization efficiencies were found to be in the range of 94−100%, and from experiments in which the dyes were added together, the decolorization efficiencies of the dye mixture were between 77% and 97% at the end of 24 h. Results of LiP and MnP activities by the fungus revealed a strong role played by the enzymes in the dye decolorization process. As compared to the previous results obtained in batch shake flasks, the results in the present study revealed excellent performance of the bioreactor in decolorizing the wastewater containing the azo dyes.