Acute occlusion of an endotracheal tube (ETT) is a feared, potentially life-threatening complication of mechanical ventilation. In the presence of a thoracic trauma, a blood clot needs to be taken into consideration as the cause of airway obstruction. This report describes a case of sudden ventilation failure due to acute ETT obstruction by a blood clot caused by intrapulmonary haemorrhaging in a child following multiple trauma accompanied by blunt thoracic trauma in the absence of dyspnoe or haemoptysis.