Malignant struma ovarii is a rare ovarian teratoma consisting predominantly of thyroid tissue. Herein, we report the case of a young woman with no history of coitus and with Graves’ disease who was ultimately diagnosed with coexistent malignant struma ovarii and papillary thyroid carcinoma. The patient underwent surgery, including unilateral salpingooophorectomy and single-port robotic bilateral total thyroidectomy. To ensure future fertility, oocyte cryopreservation was performed preoperatively. She also underwent postoperative radioactive iodine therapy and was stable postoperatively.