Advanced oxidation processes (AOPs) have been used as an alternative and effective option for treatment of wastewaters especially in case of non–biodegradable compounds. It is well known that bismuth vanadate shows photocatalytic activity. In the present work, bismuth vanadate–MWCNT composite was used for degradation of toluidine blue. The degradation was monitored spectrophotometrically. Effect of different operational parameters like pH, concentration, amount of composite, light intensity, etc. was studied on the rate of degradation. A suitable mechanism for the photocatalytic degradation of toluidine blue dye has been proposed. It is an eco-friendly method for the treatment of polluted water. The catalyst can be recycled and used again.