Struma ovarii is an ovarian teratoma predominantly composed of thyroid tissue. It is usally benign but 5%–10% shows malignant changes. We report here a case of palpable ovarian mass in a young 25 years old woman who underwent left salpingo oophorectomy. And the specimen was diagnosed as Struma ovarii in histopathological examination. Most of the time it is asymptomatic but it may present with hyperthyroidism, or in rare cases it can be malignant papillary thyroid carcinoma. This case is reported here for its rare presentation