Thoracic aortic dissection is a life-threatening diagnosis, which should not be missed. We present a case in which a patient who presented to the emergency department with chest pain was assessed and referred for admission for treatment of pneumonia, due to misinterpretation of a chest radiograph finding. The patient was re-reviewed and subsequently underwent further investigation, which confirmed aortic dissection. She underwent emergency thoracic endovascular aortic graft repair with stent graft insertion. This case demonstrates haemothorax as an uncommon complication of aortic dissection.