Herlyn–Werner–Wunderlich Syndrome (HWWS) is a rare congenital Mullerian duct anomaly, characterized by the presence of an obstructed hemivagina with uterus didelphys and an ipsilateral renal anomaly (OHVIRA). Ovarian serous adenocarcinoma is a type of epithelial ovarian cancer and accounts for about 90% of all ovarian cancers. The incidence of Müllerian duct anomalies associated with ovarian cancer is unknown. Due to its rarity of these conditions, diagnosis and management are challenging. In this paper, we present a case of a 53-year-old, nulligravid woman who presented with an acute abdomen. A transrectal and transabdominal sonography showed an ovarian mass with malignant features. Immediate surgical intervention was performed, and removal of the ovarian mass was done. Intraoperatively, findings of obstructed hemivagina, uterine didelphys, and the absence of one kidney were noted, suggestive of HWWS. Biopsy of the mass revealed borderline serous cystadenocarcinoma of the right ovary.