The study of nanocomposites is an interdisciplinary area, including physics, chemistry, biology, materials science, and engineering. The surface area/volume ratio of reinforcement materials employed in the preparation of nanocomposites is crucial to the understanding of their structure-property relationship. Different types of cellulose at the nanometric scale have been used as precursors for obtaining nanocomposites. The use of nanocellulose as a filling material has attracted the attention of researchers because it presents a series of advantages, such as, biodegradability, low density, large specific surface area, high relative abundance, easy processability and a wide reactive surface allowing for easy modification. Pharmaceutical and biomedical applications of cellulose-based nanocomposites are very wide and have been described in terms of their biocompatibility and hemocompatibility. In biomedicine, applications of nanocellulose for composites includes tissue engineering and cellular culture, drug delivery, medical implants and substitute materials, wound healing dressings, and antimicrobial materials.