Rupture of the thyrocervical trunk aneurysm into the thoracic cavity does not occur very often. It is an urgent condition due to hemorrhagic shock by massive hemothorax with potentially fatal consequences. Pregnancy and puerperium are additional risk factors for a rupture of the thyrocervical trunk aneurysm in patients with neurofibromatosis and aneurysms. This is the first case of thyrocervical trunk aneurysm rupture after a Cesarean section in a patient with neurofibromatosis type I noted down in the literature. The patient, a 33-year-old woman with neurofibromatosis type I, three days after an already performed Cesarean section had acute pain in the left area of the neck, swelling, and a hematoma that progressed rapidly to respiratory distress, hemothorax, and hemorrhagic shock. Emergency endotracheal intubation was performed for airway control. Urgent computer tomography angiography procedure showed extracranial artery, thyrocervical trunk aneurysm rupture, and vertebral aneurysm without rupture. The patient was urgently and successfully treated by endovascular coil embolization of a ruptured thyrocervical trunk aneurysm and subsequently thoracic drainage for massive hemothorax. Postoperatively, her left neck pain decreased, after which she had no further neurologic deficits. The patient was discharged 10 days later. Thyrocervical trunk aneurysm rupture is a rare condition with a potential outcome of death which requires urgent intervention. Endovascular coil embolization is a minimally invasive, safe, and efficient treatment for patients with rupture of thyrocervical trunk aneurysm and following comorbidities.