Endometrioid borderline tumours (EBTs) of the ovary are uncommon, comprising about 0.2% of all epithelial ovarian tumours. Here we report a case of ovarian endometrioid borderline adenofibroma because of its rarity, emphasising on its challenging histological diagnosis and the significance of uterine curettage to exclude synchronous endometrial adenocarcinoma. A 64-year-old woman presented with post-menopausal bleeding and pan hysterectomy was performed. Uterus showed atrophic endometrium with an adenomyomatous polyp and left ovary showed a nodulocystic mass measuring 7.5 x 5 x 5cm which was diagnosed as a case of endometrioid borderline adenofibroma.