A combination of mechanical and chemical methods transforms cellulosic materials into cellulose nanocrystals (CNCs). CNCs have become a popular sustainable material owing to their enhanced features in response to the increasing global need for environmentally friendly, biodegradable and biocompatible products. Novel extraction processes, procedures, and resources are being developed to meet the increasing demand for cellulose nanocrystal-based products on an industrial scale. Cellulose nanocrystals show great potential as a biomaterial for drug delivery systems, catalysis, food processing, environmental investigations and heat transfer applications. The current review article examined the existing literature and presented a concise summary of the structural aspects, isolation methods and use of CNCs in the drug delivery system.