Acute urinary retention in a female child is rare because of its anatomy. Haematocolpos can cause a mechanical obstruction, resulting in acute urinary retention. We are presenting a case report of 13 year old female presented with complain of urine retention for 24 hours. She had no significant medical history and she had not attained menarche. Ultrasound abdomen showed hematocolpos like mass compressing the bladder. On examination; she had a palpable bladder and a bluish-grey bulge posterior to her urethral meatus. She underwent a hymenotomy using cruciate incision with drainage of the hematocolpos. Postoperatively, she made a good recovery with a successful removal of the urinary catheter. She has started normal menses and had no further urinary problems. We emphasise to include hematocolpos, even though uncommon, in differential diagnosis and should be ruled out in adolescent females with amenorrhoea and acute urinary retention.