Introduction: Mature teratoma is the most common germ cell tumor(and the most common tumor) of the ovary,composing more than 20% of all ovarian neoplasms .Super infection of dermoid ovarian cyst is very rare.

Case Report: A 72 year-old woman was admitted to the gynecological outpatient clinic because of lower abdominal pain and fever. Gynecological examination and ultrasonography revealed a heterogeneous cystic mass in the right ovary. Abdominopelvic CT scan revealed a right ovarian mass (15×15 cm) thought to be a dermoid cyst. Right adnexectomy was performed. The pathological evaluation suggested infected benign ovarian dermoid.

Conclusion: They are the most common ovarian neoplasm found in adolescence and during pregnancy. Mature cystic teratoma may be complicated by torsion, rupture, and malignant change infection of a mature teratoma is a relatively uncommon event. However, based on our case and other cases, superinfection with abscess formation should be considered in the differential diagnosis whenever a patient with a documented pelvic mass and fever refers to gynecologists.