Diabetes mellitus or diabetes is one of the leading public health problems of today’s society. Every year the number of patients with diabetes increases in Croatia and the rest of the world. People with diabetes mellitus needs the best and the earliest education about disease, complications, treatment methods and self-help. The characteristic of diabetes mellitus is high blood glucose or sugar. It is known that long-term increased blood glucose level is leading to a number of complications. One of the most severe and most frequent complication of diabetes mellitus is a diabetic foot. Due to the high level of blood glucose, peripheral blood vessels and nerves get damaged and that is causing diabetic foot ulcer or wound and infection. Treatment of diabetic foot is complex and longstanding process. Diabetic foot ulcer hardly heals and that is a reason why it is sometimes impossible to avoid amputation of the affected foot or lower extremity in addition to all taken treatment and prevention measures. However, scientific research has shown a positive effect of hyperbaric oxygen therapy which improves healing of diabetic foot ulcer and drastically reduces the amputation rate. Hyperbaric oxygen therapy is an adjuvant method for the treatment of diabetic foot that is performed in hyperbaric chambers where patient inhales approximately one hundred percent oxygen under condition of increased ambient pressure. The nurse plays a very important role in the multidisciplinary team for treatment of diabetic foot with hyperbaric oxygen therapy. The nurse should be highly educated and have extensive knowledge about working inside and outside of the hyperbaric chamber and especially about diabetes mellitus and management of diabetic foot. The role of the nurse in treatment of diabetic foot with hyperbaric oxygen therapy refers to the preparation of hyperbaric chamber, preparation and education of patient and his family about hyperbaric oxygen therapy and safety measures that have to be followed, also it refers to the monitoring of patients during hyperbaric oxygen therapy and to the diabetic foot ulcer control and management. Because of more frequent use of hyperbaric oxygen therapy in treatment of diabetic foot it is necessary to pay more attention to the improvement of nurses education and to the importance of their multifunctional role.