Background Rhino‐orbito‐cerebral mucormycosis (ROCM) is an opportunistic pathogenic fungal disease caused by the fungus mucor, and it is a life‐threatening fungal infection. The ulceration on the skin of the head and neck, accompanied by rhinitis, headache, orbital inflammation, and eyelid edema, should raise a high suspicion of Mucor infection in diabetic patients with inadequately controlled blood glucose. Case Description The clinical data of a patient with ROCM were analyzed retrospectively, and the clinical features were analyzed. The patient was admitted to the hospital with “diabetic hyperosmotic coma” after presenting with fatigue, poor appetite, and disturbances in consciousness as initial symptoms. After improving relevant examinations, controlling underlying diseases, and administering antifungal treatment, the final clinical outcome was death. Conclusion ROCM is more prevalent in patients with uncontrolled diabetes and varied clinical manifestations. The characteristic feature is an eschar‐like necrosis of the local skin or mucosa. The gold criteria for diagnosis are pathology and fungal culture; imaging examination does not reveal any specific manifestations. Early diagnosis and effective treatment are the keys. Rhino‐orbito‐cerebral mucormycosis is more prevalent in patients with uncontrolled diabetes and varied clinical manifestations. The characteristic feature is an eschar‐like necrosis of the local skin or mucosa. The gold criteria for diagnosis are pathology and fungal culture; imaging examination does not reveal any specific manifestations. Early diagnosis and effective treatment are the keys.