Azo dye has a massive marketplace in various industries, biological laboratories and clinics. A significant drawback is the excessive flush-off of azo dyes and their intermediate products are that they pollute the environment. Several environmental bacteria degrade azo dye under certain specific ecological conditions. Decolourisation by different bacteria occurs under aerobic, anoxic and anaerobic conditions. Bacterial genera such as Pseudomonas, Bacillus and Rhodococcus are used for the rapid decolourisation of azo dyes. Bacterial enzymes play an essential role in the degradation of azo dyes by cleavage of azo bonds (-N=N-). It is degraded by both oxidative and reductive enzymes including azo reductase, laccase, lignin peroxidase, NADH-DCIP reductase, malachite green reductase, polyphenol oxidase (tyrosinase), veratrol alcohol oxidase. This review describes the role and mechanism of these enzymes in the degradation of azo dyes.