FATWO (female adnexal tumors of probable Wolffian origin) is a rare group of tumors found in the adnexal region, and its origin is thought to be the Wolffian duct. Here we report a case treated with a laparoscopic surgery under a preoperative diagnosis of myoma uteri, which was postoperatively diagnosed as FATWO. A 40-year-old multiparous woman presented with right lower abdominal pain. Pelvic examination and MR imaging supported clinical diagnosis of degenerated myoma, and laparoscopic surgery was performed. At the operation, a solid tumor located in the right mesosalpinx was identified. The tumor was laparoscopically enucleated from mesosalpinx. Microscopic examination revealed a tumor showing tubular proliferation of cuboidal cells with scant cytoplasm and bland round nuclei, and the case was pathologically diagnosed as FATWO. Hysterectomy and bilateral salpingo-oophorectomy were performed later, but the removed specimen was free of tumor. The patient is well without recurrence of disease. Preoperative diagnosis of FATWO may be challenging, but FATWO should be considered as a differential diagnosis when a solid tumor was found in the leaves of the broad ligament or in the mesosalpinx. [Adv Obstet Gynecol, 67 (2) : 126-129, 2015 (H27.5)]