In this article, we present a 31-year-old female who presented with intermittent headache and oligomenorrhea of over 10 years' duration. Imaging revealed a large suprasellar mass with sellar extension. The patient underwent an endoscopic endonasal trans-sphenoidal surgery to resection of the mass. Clinical, radiological, and operative findings from this patient were initially considered to be Rathke's cleft cyst (RCC). However, postoperative histological examinations revealed a mature cystic teratoma. No radiotherapy was performed after surgery. At the most recent follow-up, approximately 1 year later, the patient is doing well with no headache and no recurrence of the teratoma.