Polycystic ovarian syndrome (PCOS) is associated with menstrual irregularities, ovulatory dysfunction, hirsutism, insulin resistance, obesity and metabolic syndrome but is rarely associated with severe hyperandrogenaemia and virilisation resulting in male pattern baldness and clitoromegaly. Total serum testosterone greater than twice the upper limit of the reference range or free androgen index of over five-fold elevated suggests a diagnosis other than PCOS. We reported a case of a 15 years old obese girl presented with secondary amenorrhoea, virilising signs: frontal baldness, clitoromegaly and prominent signs of insulin resistance and marked acanthosis nigricans. Her total testosterone level was markedly elevated at 9.4 nmol/L (0.5–1.7 nmol/L) and MRI pelvis revealed a right ovarian mass with fat and cystic component and a left polycystic ovary. The patient underwent laparoscopic right ovarian cystectomy and histologically confirmed mature cystic teratoma. Post-operatively, her testosterone level declined but did not normalise, menses resumed but remained irregular. Her fasting insulin was elevated 85.2 mIU/L (3–25 mIU/L) and HOMA-IR was high at 13.1 (>2) with persistent acanthosis nigricans suggesting co-existing HAIR-AN syndrome, an extreme phenotype of polycystic ovarian syndrome.