Mucormycosis is the most fatal systemic fungal disease which is precipitated by diabetes or immunodeficiency state. The most common form of the disease is the rhinocerebral involvement. The disease has a high rate of mortality if not diagnosed in time and treated properly. This article presents Mucormycosis in a diabetic. The case was a 26 year old young male with diabetes mellitus being treated with insulin who was presented with fever, facial and right eye swelling, general bad condition, having a 3 year history of heroin (crystal) addiction, and referred with initial diagnosis of cellulites. On examination, it was found that the case had right eye proptosis and ecchymossis, unilateral bloody discharge of nose and dispnea. Moreover, black necrotic lesion was found in nasal mucosa. Biopsy of necrotic tissue was done and staining with PAS was performed, which proved the existence of rhinocerebral mucormycosis. The patient was taken to ICU and was Administered broad spectrum antibiotic treatment and 1mg/kg amphotericin B. But the next day, in spite of the treatment, the patient got dementia and deceased three days later.