The safety and biocompatibilityBiocompatibility of a material is determined by its ability to interact with the biological system without causing adverse reactions. Regarding safety, microbiological safetyMicrobiological safety stands out, when applied to cells, chemical modification, when its derivatives are used with some modification in the cellular chain. When referring to biocompatibility, some care such as degradability, when modified for this purpose, with in vivo and in vitro studies are necessary to evaluate the real biocompatibilityBiocompatibility of the materials. CelluloseCellulose, in general, generates biocompatible and safe materials for use in the medical field. This chapter will discuss points relating to cellulose, briefly discussing how it is obtained and the challenges it faces in terms of possible contamination, its toxicityToxicity and biocompatibility, and how to proceed with assessing its safety in in vitro and in vivo models, as well as environmental toxicity analyses and regulatory guidelines on its production and use. Briefly, its application, especially in the area of biomedical engineering, has been gaining prominence in product development and its use is increasingly promising, as most studies indicate that the use of celluloseCellulose is very promising due to its high biocompatibilityBiocompatibility with organisms and its good biodegradability in the environment, including in tests with aquatic animals. However, although it is normally considered safe, whenever a new product is produced with celluloseCellulose and its derivatives, safety assessments must be carried out, as the origin of the cellulose and the method of obtaining it can influence the toxicityToxicity of the material.