A 22 year-old woman presented to our clinic with secondary amenorrhoea, pain of the right adnexal region. At ultrasound, the right ovary presented a multilocular complex mass of 10.4x8.5x7.3 cm enucleated and removed on laparoscopy. The histological diagnosis was mature cystic teratoma. Because of persisting amenorrhoea, the endocrine evaluation performed was consistent with polycystic ovarian syndrome (PCOS). Eight months later, two small left ovarian masses were removed by a second laparoscopy and the pathological diagnosis was again mature cystic teratoma. Treatment with myoinositol (MI) 550 mg + D-chiroinositol (DCI) 13.8 mg + folic acid 200 µg twice a day achieved persistent normalization of the endocrine and metabolic values over the 24 months of follow-up. To our knowledge this is an unusual case of multiple and bilateral metachronous ovarian teratomas with a co-existing PCOS.