Biodegradation of synthetic dyes, rose Bengal, nigrosin, congo red, chlorazole black E and safranin have been carried out using a fungal isolate, Aspergillus niger, isolated from coal mines. Among the 33 fungal species recovered from coal mines only A. niger was found to be a good decolourizer of dyes. This fungus has shown positive results for the decolourization of synthetic dyes. The degradation of dyes was observed by the change in original colour and visual disappearance of colour from the solution. Decolourization of dyes was also observed as accumulation of dyes by the fungal mycelium, and it was confirmed by the presence of colour in the fungal mycelium. Two types of controls: media without dye and with dye were used for studying dye decolourization.