Liposarcoma is the most common soft tissue sarcoma in adults, and it typically occurs in either the retroperitoneum or the extremities. However, this malignant tumor is very rare in the female reproductive system. A 58-year-old woman presented with acute abdominal pain, and computed tomography (CT) scan detected multiple masses measuring 4-6 cm in size with a fatty density in her adnexal region. Laparoscopic evaluation revealed tumors of the left fallopian tube with a normal left ovary. Histopathological evaluation of the resected pelvic tumors showed lipocytes and lipoblasts of various sizes, leading to diagnosis of well-differentiated liposarcoma of the left adnexal region. This is the first known case of a liposarcoma arising from the fallopian tube. When a pelvic mass with fatty density that does not show typical findings of a mature cystic teratoma is detected by either CT or magnetic resonance imaging, the possibility of a liposarcoma should be considered.