Ovarian cancer is responsible for over 140,000 deaths worldwide. Age, nulliparity and family history of ovarian cancer have been associated with increased risk. Borderline ovarian tumours are characterised by a clearly more favourable clinical course and prognosis than invasive ovarian cancer. The use of tumour markers has not proved useful in the early detection of disease, so a high level of suspicion, along with physical examination and imaging studies are the key to diagnosis. We present the case of an adolescent with a borderline ovarian tumor without previous clinical symptoms which was detected on ultrasound performed in the clinic.