Chitosan is a cationic natural polymer composed of glucosamine and N-acetylglucosamine residues that are held together by a glycosidic bond. Chitosan has many excellent properties, including physicochemical properties, i.e., stability in the natural environment, chelation of metal ions, high sorption properties, biological properties such as biocompatibility and biological activity, ecological properties resulting from biodegradability, and physiological properties, which include non-toxicity, and economic affordability, and is used in various biomedical and industrial applications. The presented article highlights recent developments in chitosan-based formulations for the treatment of bacteria, viruses, cancer, or gastroesophageal reflux disease. Moreover, chitosan-derived biomaterials can also be used in regenerative medicine or food packaging to prevent contamination by pathogenic microorganisms. In summary, this is a valuable compilation in this emerging field that focuses on the biomedical application of chitosan-based biomaterials.