Sinonasal teratocarcinosarcoma (SNTCS) is one of the rarest, aggressive malignant neoplasms of sinonasal tract, consisting of primitive neuroepithelial elements with various malignant epithelial and mesenchymal components. Previously described as teratoid carcinosarcoma, malignant teratoma, or blastoma, SNTCS constitutes less than 1% of all cancers and approximately 3% of all malignancies of head and neck region, which is mainly located in the nasal cavity and paranasal sinuses, although tumors occurring in other locations including the nasopharynx and oral cavity have been described. Here, we are presenting a 22-year-old patient with SNTCS involving the nasal cavity, nasopharynx, and all paranasal sinuses with bilateral orbital and intracranial extension treated with surgery followed by radiotherapy and chemotherapy. [ABSTRACT FROM AUTHOR]