In this paper, we report the experience of providing nursing care for a patient with moderate mental retardation who was admitted for type 1 diabetes treatment. Because the patient had moderate mental retardation, the patient's mother, who independently provided care for the patient and had limited knowledge of care and this disease, was considerably anxious and required help. During hospitalization from June 6th, 2016, to June 21st, 2016, the nursing staff performed a full care evaluation and found that the patient had an unstable blood glucose level and received ineffective health maintenance and that the caregiver was under considerable stress regarding providing care. During the nursing process, considering the intelligence level of the patient, we used conversational reading skills and individual picture books to provide information regarding diabetes-related self-care skills to the patient. We simultaneously attempted to reduce the mother's care burden. Finally, at the time of discharge, the patient had a stable blood glucose level and the mother was confident in providing care for the patient. After discharge, we continued to provide follow-up care to help the patient maintain a stable condition.