Acute occlusion of the left internal mammary artery (LIMA) immediately following coronary artery bypass surgery (CABG) is a rare complication that is usually treated by repeat emergency surgery. We described the case of a 65-year-old man known for dyslipidemia and family history of coronary artery disease who was admitted for non-ST elevation myocardial infarction as a result of a severe stenosis of the left anterior descending (LAD) coronary artery. After the discussion within the Heart Team, the patient underwent CABG with LIMA to LAD. As intraoperative blood flow control by transit time flowmeter showed intermittent flow despite optimal anastomosis, immediate coronary angiogram was performed following CABG and an occlusion of the LIMA graft was documented. By contrast injection though a microcatheter advanced into the occluded LIMA it could be demonstrated that the anastomosis was patent and that flow was obstructed by a focal lesion, most likely due to a bend/torsion of the LIMA or a focal vessel wall hematoma. Following multidisciplinary discussion within the Heart Team, a percutaneous coronary intervention (PCI) with a drug eluting stent of LIMA was performed with a good angiographic result and normalization of the flow. The clinical course of the patient was uneventful. This case suggests that, in selected cases, emergent PCI may be an alternative to repeat-CABG in patients with acute perioperative LIMA occlusion.