Mucinous borderline ovarian tumors (BOTs) occur most often in women between the ages of 20 and 30. Early-stage detection of the condition has a more favorable prognosis. In this case report, the authors present an elderly 93-year old woman who visited our hospital due to severe abdominal pain after being diagnosed with a pelvic mass 2 years ago and not undergoing any treatment since the diagnosis was made. She underwent emergency left salpingo-oophorectomy and was diagnosed with mucinous BOT according to biopsy results.