OBJECTIVE: Sinus teratocarcinosarcoma is an extremely rare malignant tumor that arises from epithelial pluripotent olfactory cells in the nasal cavity. It consists of neuroectodermal, epithelial, and mesenchymal proliferations of variable degrees of maturation. The presence of fetal squamous cells with clear cytoplasm is considered as a pathognomonic histopathological finding. Clinically, the patients present with recurrent epistaxis and nasal obstruction, but other symptoms may arise as anosmia, epiphora, mental disturbances, proptosis, and visual loss, depending on the extent of tumor growth. Herein, we report the case of a young patient with a teratocarcinosarcoma, who presented to the Service of Otorhinolaryngology of Hospital das Forças Armadas - DF. CASE REPORT: A 13-year-old male patient presented complaining of nasal obstruction for the past 4 years and recurrent epistaxis since childhood. The physical examination revealed a lesion in the right nasal cavity with nostril externalization. Computed tomography of the skull and paranasal sinuses revealed a lesion occupying the entire right nasal cavity and right maxillary sinus with no bone erosion. The lesion was not detectable by CT angiography with contrast enhancement. The lesion was excised surgically. Histopathological analysis identified the lesion as malignant and poorly differentiated. The immunohistochemical analysis yielded a diagnosis of teratocarcinosarcoma. The patient is currently under treatment with chemotherapy in the oncology department. CONCLUSION: A teratocarcinosarcoma is a malignant neoplasm that should be considered in the differential diagnosis of tumors of the nasal cavity in young people complaining of nasal obstruction and recurrent epistaxis. Early diagnosis is important due to the aggressiveness of the tumor, which may compromise the patient's prognosis.