Introduction: Tailgut cyst (retrorectal cystic hamartoma) is an uncommon congenital lesion that arises from remnants of the embryonic post-anal gut. It is usually benign and located in the retrorectal/presacral space. Case report: A 45-year-old woman presented with lower abdominal discomfort, urinary frequency and right-sided pelvic mass. Digital rectal examination and computerized tomography scan demonstrated a multicystic complex mass occupying the region of the right ovary and extending into the retrorectal/presacral space. The initial diagnosis was neoplasm of the right ovary. At laparotomy, the mass was lying free from apparently normal internal genital organs. Excision of the mass from the right pelvis and retrorectal/presacral space and total abdominal hysterectomy were performed. Microscopic examination revealed that the wall of the cystic mass consists of a lining epithelium composed of columnar and squamous epithelium and a stroma composed of fibrous tissue containing scattered discontinuous bundles of smooth muscle fibers. Based on these histological findings, the final diagnosis was tailgut cyst. Conclusion: Tailgut cyst is an uncommon entity that should be included in the differential diagnosis of retrorectal/presacral mass. The treatment of choice is complete surgical excision.