The authors report a case of percutaneous transluminal angioplasty (PTA) with coronary stent for stenosis in a left internal mammary artery (IMA) graft, which led to newly developed stenosis at both sides of the stent in the IMA graft. The intravascular ultrasound (IVUS) revealed that the stenotic lesion consisted of intramural hematoma, which had shifted owing to the stent deployment. They suggest that the cause of stenotic lesions in IMA grafts at the early postoperative period is luminal compression by intramural hematoma, which can be visualized by use of IVUS. The strategy of PTA for IMA grafts performed at the early postoperative period should include consideration for hematoma shift.