The ongoing development of manufacturing technologies and of biocompatible and biodegradable polymers have significantly contributed to the progress of drug delivery systems. In the last decades, the knowledge on keratins has significantly increased, regarding their ultrastructure, molecular and cell biology, physiological and pathological roles, as well as their practical applications in the biomedical field. Produced through sustainable, simple and cheap methods, the natural, non-toxic keratin is one of the raw biomaterials frequently used in the pharmaceutical technology for different applications. The purpose of this review is to present the keratins ultrastructure, types, biological distribution, tissue expression profiles, some of their multiple physiological and pathological roles, as well as their practical applications in drug delivery and cellular and tissue engineering.