Mature cystic teratoma (MCT) is a benign and unilateral ovarian neoplasm usually seen in premenopausal women. Its most common complication, torsion, is a well-known cause of acute abdominal pain. However, it is rare in the early postpartum period. In this paper, we present a case of ovarian torsion due to MCT, which was diagnosed radiologically in the early postnatal period and surgically confirmed. A 25-year-old woman vaginally delivered a healthy baby on time and without any problems. She presented with acute abdominal pain in the right lower quadrant on the postpartum 5th day. Abdominal ultrasound (US) and computed tomography (CT) demonstrated an ovarian mass containing fat and calcification in the right adnexa and non-enhancing ovarian parenchyma. The patient was discharged on the 5th day after the salpingo-oophorectomy operation without any complications. US and CT provided crucial information to make an accurate and rapid management decision in ovarian torsion due to MCT.