Mature cystic teratomas are common benign ovarian tumors. They usually occur in young women, less than 40 years old. Our case report concerns a patient of perimenopausal age who came to the hospital complaining about mild abdominal pain, fever below 37.8°C, and diarrhea. The patient had an intrauterine contraceptive device inserted. Based on the clinical findings and imaging, a possible diagnosis of pelvic inflammatory disease was set, and intravenous administration of broad-spectrum antibiotics started immediately. The decision for performing laparotomy was taken after the fact that the clinical condition and blood tests of the patient had shown no improvement. Intraoperatively, the presence of a large twisted ovarian mass with signs of total necrosis due to adnexal torsion was detected. A histological examination of the surgical specimen confirmed the diagnosis of mature cystic teratoma in the right ovary. The postoperative course was uneventful. The presentation of the case follows a brief literature review of this rare medical condition regarding the diagnostic and therapeutic approach of these patients.