PURPOSE: Mucormycosis generally occurs in patients with uncontrolled diabetes mellitus and immunocompromised conditions. It is rare, but once a patient is infected with it, it can occur as a rapidly extending, aggressive, and life-threatening rhinocerebral infection with a high mortality rate. METHODS: A 70-year-old female patient had a 40 years of history of adult onset diabetes mellitus. She presented herself with severe right hemifacial pain, swelling, and weakness for 3 days and was admitted to ENT. On a facial computed tomography(CT) scan, it was found that her infection extended from her inferior temporal scalp to her submental area and involved her submandibular, masseter, prevertebral, parapharyngeal, retropharyngeal, and pharyngeal mucosal space and pansinusitis. Through endoscopic sinus surgery, mucormycosis was confirmed via histologic examination. RESULTS: Despite empiric antibiotics and amphotericin B administration, the patient was in a septic condition and in a coma. The patient's family wanted to withdraw her life support, and the patient expired. CONCLUSION: Mucormycosis is very rare, but is one of the disastrous complications of uncontrolled diabetes mellitus. Suspicion of its occurrence, based on identified risk factors, and its rapid diagnosis can enhance the chance of its cure.