In recent years, bio fibers (such as jute, hemp, flax, nettle, etc) are gaining more attention due their light weight, high specific strength, biodegradability, etc in various applications. Along with this, environmental issue is also an important aspect for maintaining sustainability of the bio fiber based composites. Failure occurs in bio fiber based polymer composites when they are applied to severe loading conditions and the material start degrading. To sustain the lifetime of the bio fiber composites, chemical treatment of the bio fiber is done to enhance the mechanical strength between the bonds so that the amount of stress transferability in the composites is equalized. The most important chemicals sources for the treatments are alkaline, silane, acetylation, benzoylation, acrylation, maleated coupling agents, permanganate, peroxide, isocyanate, stearic acid, sodium chlorite, triazine, derivatives of fatty acids (oleoyl chloride). The present study summarises the studies carried out on the environmental impact and various chemical treatments that were applied to bio fibers for enhancing their properties.