Blunt thoracic trauma often causes rib fractures, hemothorax, and pneumothorax. Although there is no established definition regarding the duration and management of delayed hemothorax, it commonly occurs in a few days and exhibits at least one displaced rib fracture. Moreover, delayed hemothorax rarely develops tension hemothorax. A 58-year-old male who had a motorcycle accident received conservative treatment from his orthopedic doctor. He felt a sudden severe chest pain 19 days after the accident. Contrast-enhanced computed tomography (CT) of the chest revealed multiple left-sided rib fractures without displacement, left pleural effusion, and extravasation near the intercostal space of the seventh rib fracture. After transfer to our hospital and a plain CT scan, which showed a more mediastinal shift toward the right, his condition deteriorated with cardiorespiratory embarrassment, such as restlessness, hypotension, and neck vein distention. We diagnosed him with obstructive shock due to tension hemothorax. Immediate chest drainage ameliorated restlessness and elevated blood pressure. Here, we report an extremely rare and atypical case of delayed tension hemothorax after blunt thoracic trauma without displaced rib fractures.