Mature cystic teratoma is the most common kind of ovarian germ cell tumor. Malignant transformation is uncommon, with thyroid cancer rarely found. Papillary thyroid microcarcinoma has rarely been described as associated with ovarian teratomas. We report a case of a 34-year-old woman who presented with abdominal pain and an ovarian mass. After surgery, the patient was diagnosed with a follicular variant papillary thyroid microcarcinoma that arose within a mature cystic ovarian teratoma. Based on the small size of the primary lesion and patient preferences, no further treatment was performed. To our knowledge, this is the third reported case of papillary thyroid microcarcinoma arising within a mature ovarian teratoma without struma ovarii. There is no consensus on the surgical approach and postoperative management of this condition. Whether further therapy with total thyroidectomy and radioiodine ablation may be beneficial is unknown. In conclusion, papillary thyroid microcarcinoma can also arise within mature ovarian teratomas. Although a favorable prognosis is anticipated, there is limited information about its history or prognosis.