BACKGROUND There is now evidence to support that some cases of high-grade serous papillary carcinoma arise from the fallopian tubes rather than the ovaries. Common symptoms at presentation include abdominal pain and swelling, vomiting, altered bowel habit and urinary symptoms. To our knowledge, this is the first case of serous papillary carcinoma presenting as a vaginal mass lesion. CASE REPORT A 41-year-old woman was referred to the Bnai-Zion Medical Center with the main complaint of irregular vaginal bleeding, vaginal mucous discharge, and suspected pelvic mass. Physical examination showed a soft, painless mass, measuring about 10 cm in diameter located mainly in the recto-vaginal septum, but not involving the uterus. Ultrasound examination showed no abnormal ovarian or uterine findings. Transvaginal biopsies of the mass showed a poorly differentiated serous papillary carcinoma of ovarian, tubal, or peritoneal origin. The physical examination and imaging findings strongly indicated an inoperable tumor, and the patient was treated with neoadjuvant (pre-surgical) chemotherapy. Pre-operative computed tomography (CT) imaging showed the partial involvement of the colon, and so surgical treatment included total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, partial vaginectomy, anterior rectal resection, and lymph node dissection. Histopathology of the surgical specimens showed a poorly differentiated serous carcinoma originating from the fimbria of the right fallopian tube. CONCLUSIONS To the best of our knowledge, this is the first report to describe primary fallopian tube papillary serous carcinoma presenting as a vaginal mass. Therefore, physicians should be aware of this possible diagnosis.