Background <p>Anomalous origin of the left coronary artery from the pulmonary artery is a rare congenital heart defect associated with high mortality during infancy if not surgically corrected. Its occurrence combined with hypoplastic left heart syndrome is highly uncommon, presenting considerable diagnostic and technical challenges. Identifying such an anomaly before surgery can be challenging, particularly in patients with complex cardiac anatomy. Intraoperative recognition requires immediate adjustments of the surgical approach, especially regarding myocardial protection and coronary artery reconstruction.</p> Case Presentation <p>A female infant was delivered at 39 weeks of gestation with a birth weight of 3038&#xa0;g. She was prenatally diagnosed with a variant of hypoplastic left heart syndrome, which was characterized by mitral and aortic stenosis, double-outlet right ventricle, and moderate tricuspid regurgitation. At birth, she underwent bilateral pulmonary artery banding to manage heart failure symptoms. Preoperative imaging did not provide sufficient visualization of the coronary arteries. At 15 days of age, she underwent the Norwood procedure with right ventricle-to-pulmonary artery shunt and tricuspid valve repair. During surgery, it was observed that the left coronary artery originated from the right pulmonary artery. To maintain coronary perfusion, a cannula was inserted into the main pulmonary artery, connecting it to a cardiopulmonary bypass circuit. Subsequently, the left coronary artery was reimplanted into the neoaorta to preserve alignment and minimize tension. The postoperative course included extracorporeal membrane oxygenation for 3 days because of right ventricular dysfunction, with sternal closure on postoperative day 13. At 7 months, she underwent a bidirectional cavopulmonary shunt. At 2 years of age, she continues to be monitored on heart failure medication and exhibits a stable clinical status.</p> Conclusions <p>In patients with complex congenital heart disease, a thorough assessment of the coronary artery anatomy is essential for surgical planning. In cases of unfeasible preoperative diagnosis, prompt intraoperative management must ensure myocardial protection and long-term coronary artery function. This case demonstrates that careful intraoperative decision-making can lead to successful outcomes, even in cases of unexpected anatomical findings.</p>