Mucinous cystadenomas are among the most common benign ovarian neoplasms. They are known for their massive size causing compressive effects ranging from pressure, pain, bloating, and urinary symptoms. Over time, these adnexal masses can lead to fatal complications, such as ovarian torsion or hemorrhage. Incidental findings of these tumors are common as many of these patients are asymptomatic. Pelvic examinations and imaging studies can be used to further diagnose symptomatic patients and aid physicians in developing an appropriate course of treatment. We report a rare case of a large mucinous cystadenoma, with a size of 25 × 25 cm and concurrent management of postmenopausal bleeding. We present the data from the admission of the patient to her discharge, including history and physical examination, diagnostic reports, transabdominal ultrasound, CT scan, surgical evaluation, and surgicalpathology reports. Abdominal pain can present in a variety of different scenarios, and ovarian masses only represent a small portion of the differentials. Mucinous cystadenomas constitute an even smaller percentage of these ovarian growths. As discussed in this case report, a large ovarian mucinous cystadenoma was compressing the surrounding structures resulting in a wide array of symptoms. The case describes the importance of extensive diagnostic evaluation and prompt surgical management of these ovarian tumors. It also brings attention to the significance of diagnosing a medical condition such as postmenopausal bleeding promptly to avoid potential negative outcomes.