Petroleum-based synthetic materials and product expansion has become a major concern due to its ecological and environmental implications. Hence, there is a pressing need for the development of novel, efficient, cheap and eco-friendly synthetic materials. Advancements in the field of nanobiotechnology, biopolymer nanocellulose has received a lot of attention due to its easy availability from plant species and remarkable characteristics like biocompatibility, high aspect ratio and renewability. Nanocellulose can be synthesized from cellulosic agricultural waste like rice husk, sugarcane bagasse, tea leaves, etc., by employing mechanical, physicochemical, chemical and enzymatic pretreatment methods. Hydroxyl functional groups abundance mediates surface functionalization of nanocellulose by hydroxyl functional groups acetylation, etherification, silylation, amidation and urethanization. Drug delivery, tissue engineering, wastewater treatment, flame retardants are the wider applications of nanocellulosic materials. This chapter focuses mainly on the synthesis, modifications of the surface of nanocellulose and their wider applications.