Huge primary teratoma in the preperitoneal space is an extremely rare clinical entity and can be easily misdiagnosed as tumors of the intraperitoneal or pelvic origin. We report a case of primary huge mature teratoma in the preperitoneal space in a 74-year-old women, and reviews the clinical data and the diagnosis and treatment of this case. The patient underwent complete resection of the teratoma, which was the optimal treatment option. The patient was followed-up for 10 months and no signs of recurrence were found, suggesting a favorable prognosis.