Introduction Mixed germ cell tumors are uncommon tumors that contain two or more types of malignant, primitive, or germ cell components. This study aims to report a rare case of extragonadal mixed germ cell tumor of the sacrococcygeal area. Case report A 4-year-old female presented with lower back swelling for two weeks. It was associated with pain and fever. Investigations showed elevated Alpha-fetoprotein and normal beta HCG levels. Magnetic resonance imaging showed a large well defined heterogeneous mass at the midline of the lower coccygeal region, which displaced the rectum anteriorly without invasion. Surgical dissection of the mass with excision of the coccyx was performed. Afterward, the patient was referred to an oncology center for chemotherapy. Discussion The emergence of extragonadal germ cell tumors may be caused by a disruption in the migration of primordial germ cells along the urogenital ridge, which then undergo a malignant transformation as a consequence of their microenvironment. Another idea states that extragonadal germ cell tumors occur when germ cells that routinely migrate into the extragonadal region during embryogenesis undergo malignant transformation.