Keratinase enzymes are protein hydrolyzing enzymes belonging to the serine hydrolase group and act specifically on keratin proteins to degrade them. Since keratin proteins are present in hair, hoofs, nails, beaks, animal skins, feathers and most of our green wastes, leaving them untreated may lead to environmental pollution. So, treating such material with keratinase enzyme in order to reduce environmental pollution is one of the striking applications of keratinase enzymes. Other applications may include dehairing, use in cosmetics, drugs, clothing and biofuel production. In this study, major focus has been given to applications of keratinases; however, the methods and sources of isolation of keratinase enzymes from different microbial sources has also been discussed. Bacteria as well as fungi possess the ability to produce extracellular keratinases which may be isolated and applied to several industrial sectors. Substitution of chemical agents with keratinase has been emphasized because in comparison to chemicals, keratinase enzymes are eco-friendly, biodegradable, do not produce harmful by-products and give very efficient results.