HIV/AIDS coordinator nurses (CNs) are key professionals in ensuring the provision of quality health care to patients with HIV/AIDS and to their families. Through this case study, the functions of the HIV/AIDS CN in Japan were identified, and an initial model of the HIV/AIDS CN role was developed. Four categories of responsibility were identified: (a) assessment, (b) diagnosis of nursing problems, (c) coordination, and (d) other related nursing activities. The category of other nursing activities included four subcategories. These were (a) consultation, (b) patient education, (c) expansion of the patient's support network, and (d) administrative or office work. These categories and subcategories contribute to an understanding of the role of the HIV/AIDS CN.