Mucormycosis is a potentially life-threatening and emerging angioinvasive fungal infection with a high mortality rate. Mucormycosis is caused by the ubiquitous filamentous fungi of the Mucorales, order of the class of Zygomycetes. They commonly occur in patients with uncontrolled diabetes mellitus, renal insufficiency, organ or stem cell transplant, malignancy, chronic use of iron-chelating agents and immunocompromised patients. Mucormycosis is being increasingly recognized in India as well, mainly in patients with uncontrolled diabetes or trauma. The infection is acquired by the inhalation of spores or by direct inoculation of the fungus into the damaged skin or mucosa. The common reported sites of mucormycosis are the sinuses, lungs and skin. The difficulty and delay in diagnosis due to its rarity usually results in a poor prognosis. To reduce the mortality and morbidity, early diagnosis and aggressive treatment are very important. We report a case of oral mucormycosis in a patient with diabetes mellitus involving the nasal cavity and maxillary and ethmoidal sinuses eroding the hard palate.