Coronary artery aneurysms (CAAs) are found in a small percentage of coronary angiograms, with left main coronary artery (LMCA) aneurysms being the least common. We present a 63-year-old male patient with a history of chest pain and an abnormal nuclear stress test. Cardiac catheterization showed a large LMCA aneurysm with unusual quadfurcation left main (LM) anatomy, but otherwise showed no evidence of obstructive coronary artery disease. The patient remained clinically stable, and a repeat cardiac catheterization 2 years later showed unchanged coronary anatomy. Further medical management with close observation was elected. This case illustrates that in select cases, large LMCA aneurysms can be successfully managed medically without surgical or percutaneous interventions. To our knowledge, this is the first report of LMCA aneurysm with quadfurcation anatomy. In addition to the case description, a review of the literature is provided.