Bio-fertilizers are one of the important components of modern agriculture. Bio-fertilizers are applied in the agricultural fields as a substitute to our conventional fertilizers containing compost, household wastes and green manure. Conventional fertilizers being less effective than chemical fertilizers are not preferably used by farmers and they often try to use chemical fertilizers in the field for crop improvement. The chemical fertilizers on the other hand are not eco-friendly. They negatively affect the environment by diluting the quality of water, air and soil and can spread cancer causing agents. Moreover, they may destroy the fertility of soil in the long run. Bio-fertilizers contain microorganisms which promote the adequate supply of nutrients to the host plants and ensure their proper growth and development. Only those microorganisms are used which have specific functions to enhance plant growth and reproduction. Bio-fertilizer being essential components of organic farming play’s vital role in maintaining long term soil fertility and sustainability.