Sinonasal teratocarcinosarcoma (STCS) is a rare, morphologically heterogeneous and highly aggressive tumour of ambiguous origin. It is characterized by the presence of benign and malignant epithelial, mesenchymal and neuroectodermal components. Because of their rarity and heterogeneity, these lesions are often misdiagnosed, leading to management difficulties. Adequate sampling with a high index of suspicion is needed to diagnose this rare tumour. We reported here a 48-year old man with right nasoethmoidal mass eroding the cribriform plate with intracranial extension. An initial incisional biopsy was performed and a diagnosis of craniopharyngioma was made. Subtotal endoscopic excision of the mass revealed features of STCS. Immunohistochemistry confirmed the same. The patient was subsequently treated with radiotherapy. The histogenesis, histopathological features, immunohistochemistry findings, clinical features and treatment were discussed here. Till date, there are less than 100 cases reported in English literature.