We report the case of a 66-year-old man who died of fatal delayed hemothorax after blunt trauma to the chest. When the deceased was transferred to the hospital, his vital signs were stable; hence, medical attention was focused only on the fracture on right ankle. Three days after the orthopedic surgery, he became unsettled with symptoms similar to delirium and exhibited unstable vital signs; he then suddenly died. On autopsy, a beveled fracture was identified on the posterior aspect of the left second rib with hemothorax. It was because of a rupture in the intercostal artery at the fracture site that a simple fracture in a rib, following a blunt chest trauma can be a potentially life-threatening condition. We suggest that a meticulous examination should be performed at the rib fracture sites when a blunt trauma to the chest is suspected even when there are no internal organ injuries identified except hemothorax.