Tetralogy of Fallot (TOF) with total anomalous pulmonary vein connections (TAPVC) is a rare type of complex congenital heart disease among all TOF cases. Co-presentation of major aortopulmonary collateral arteries (MAPCAs) compensates for the lack of central pulmonary blood flow and decreases the severity of right-to-left shunting in TOF. We present a case of a 2-year-old child with complex diagnoses of TOF, TAPVC, a large secundum atrial septal defect (ASD), and intraoperatively identified MAPCAs. She underwent surgery to repair the TAPVC, valve-sparing reconstruction of the right ventricular outflow tract, interventricular defect closure, and the creation of patent foramen ovale (PFO). After the operation, hemodynamic instability happened along with sudden blood pressure drop, desaturation, and increased central venous pressure, which subsided after administering inhalational nitric oxide (NO). A postoperative pulmonary hypertension crisis was suggested when the patient experienced recurrent symptoms after the termination of NO. Echocardiographic findings of a D-shaped left ventricle (LV), right-to-left PFO shunt and high tricuspid valve gradient firmly established the diagnosis. It was subsequently managed with continuous NO inhalation and sildenafil, which rendered a satisfactory outcome. Repaired TOF and TAPVC could be at particular risk of developing pulmonary hypertension crisis, especially in the presence of MAPCAs due to possible remodeling of the pulmonary vasculature. Furthermore, a relatively noncompliant LV function and small left atrial size may exacerbate the risk of developing postcapillary pulmonary hypertension after TAPVC repair. A successful postoperative outcome calls for a meticulous preoperative analysis of the anatomical lesions, as well as careful monitoring. [ABSTRACT FROM AUTHOR]