Female adnexal tumour of Wolffian origin (FATWO) is a rare tumour arising from persisting remnants of mesonephric duct. World-wide less than 100 cases have been reported. Diagnosis of this tumour is mainly post-operative based on histopathological examination and Immunohistochemistry (IHC) markers. We report this rare case in a 48 year old woman. She was diagnosed, pre-operatively, to have left ovarian mucinous cystadenoma by radiology imaging. Post-operatively, histopathological examination reported this tumour as FATWO arising from the left broad ligament. The diagnosis was confirmed by IHC markers. Further mutational studies were also carried out. According to the literature search, this is the third case reported in INDIA, until now. Rarity and varied presentation of this tumour, makes the pre-operative diagnosis difficult. If sufficient numbers of these cases are reported, pre-operative investigations, treatment and follow-up protocols for this tumour can be formulated.