Pneumothorax is one of the most frequent complications of percutaneous central venous catheterization. Most significant pneumothoraces are easily detected on postcatheterization chest radiograph. However, we report a rare case of delayed tension pneumothorax detected 4 days after unsuccessful central venous catheterization via the infraclavicular subclavian vein, although initial postcatheterization and postoperative supine chest radiographs showed no active lesion.