Hemothorax is a possible immediate complication of central venous catheterization. We experienced a patient who suffered from massive hemothorax 72 hours after right subclavian venous catheterization. A 29-year-old female patient with Marfan's syndrome underwent the Bentall's operation and aortic arch replacement with an artificial graft, which was performed uneventfully. She recovered favorably in the intensive care unit and was transferred to the general ward on postoperative day 3. Immediately after the removal of the catheter in the general ward, massive hemothorax developed and emergent thoracotomy should have been performed to control bleeding. We report this case to re-emphasize the careful monitoring even after removal of central venous catheter and the need for ultrasound guidance during insertion of central venous catheters.