Background The coronary artery anatomy in patients with transposition of the great artery (TGA) is a contributing factor for outcome in arterial switch procedure. Case Presentation A full-term, 7-day-old baby boy diagnosed as dextro-TGA (dTGA) with intact ventricular septum. Intraoperatively, the left coronary sinus had a blind indentation from which a firm cord-like left main coronary artery originates. Procedure completed as usual for a routine arterial switch operation. Conclusion About 5% of patients with D-TGA have a single coronary artery. Assessment of blood flow to all branches intraoperatively is mandatory to choose between either transfer of single ostium or bypass grafting to the other coronary system.