Mature ovarian cystic teratoma, also known as the dermoid cyst, is one of the most common benign ovarian neoplasms that can occur in different age groups and could appear in various sizes. Diagnosing this problem as soon as possible is essential due to complications that can coincide, such as torsion, rupture, internal hemorrhage and malignant transformation. In this article, we reported a 66-year-old female patient with a single huge mature ovarian cyst teratoma who presented to the surgical ward with abdominal pain and swelling but did not see any doctor during that period and disregarded her problems for 4 years.