Ovarian cysts are rare in children. Their common presentation is acute abdomen, which can be a life-threatening event that needs emergent investigation and intervention. Herein, we report a gynaecological case of a twisted ovarian cyst in an 11-year-old girl who presented to the emergency department with sudden-onset generalised abdominal pain. Multiple strong analgesics were prescribed, and pain-controlled analgesia was then started. Abdominal ultrasound revealed a left adnexal mass, and abdominal computed tomography showed a non-enhancing soft tissue tumour with multiple cystic components in the pouch of Douglas. The patient underwent emergency laparotomy, which revealed a gangrenous left ovarian mass measuring 9×5 cm that was twisted five times. Histopathology showed extensive haemorrhagic infarction with no remnant of viable tissue, consistent with a twisted ovary. It was challenging to determine the origin of the pain in this patient, as thorough examination could not be performed because she was in severe pain. Abdominal ultrasound helps guide diagnosis, as a gynaecological cause is rare in premenarchal children. A vigilant assessment is important to avoid delays in diagnosis and emergency intervention.