BackgroundCoronary artery bypass grafting (CABG) surgery is a common procedure for managing multi-vessel coronary artery disease to revascularize the myocardium. Among the various conduits used, the left internal mammary artery (LIMA) is preferred due to its better long-term patency rate. However, CABG procedures involving LIMA may result in rare but serious complications, such as avulsion of the LIMA post-CABG, which leads to disruption of blood flow to the myocardium and the development of fatal cardiac tamponade.Case presentationWe hereby present a unique case of spontaneous avulsion of a LIMA graft to the left anterior descending artery (LAD) away from the site of anastomosis, twenty-four hours following CABG surgery in a 67-year-old male patient. Emergency re-exploration and repair of the LIMA with interposition vein graft were performed and resulted in successful stabilization of the patient’s critical condition. However, this was followed by a complicated recovery period involving atrial fibrillation, acute kidney injury, and wound infection.ConclusionAvulsion of LIMA graft following CABG is rare, yet a fatal complication that requires high clinical suspicion and prompt management. Avulsion has been reported a few times in literature following both minimal invasive and conventional CABG. Understanding the etiology, clinical presentation, and management of this complication is crucial to avoid catastrophic outcomes.