Although the use of vasopressin has become commonplace in pediatric patients with vasodilatory shock after cardiac surgery, its efficacy and hemodynamic effects have not been systematically documented. Furthermore, previous studies were mainly limited patients with left heart anomalies. To date, the use of vasopressin in patients with right heart anomalies has not yet been reported. To clarify the hemodynamic effects of vasopressin on pediatric patients with vasodilatory shock after cardiopulmonary bypass, 70 consecutive patients, most of whom with right heart anomalies, were retrospectively analyzed in Fuwai Hospital from October 2013 to September 2015. Vasopressin was administered continuously at a dose of 0.0002 to 0.002 u/kg/min. Hemodynamics, urine output, and catecholamine vasopressor doses were compared before and after vasopressin initiation. Results showed that besides the significant increase in blood pressure at 2 h after vasopressin administration, the systemic vascular resistance index also prominently elevated from 894.3 ± 190.8 dyn/s to 1138.2 ± 161.4 dyn/s per cm5 per m2, while the heart rate, right atrial pressure, pulmonary artery pressure had a trend of decline. Subsequently, the fluid requirement, the catecholamine vasopressor requirement both decreased and urine output increased. Lactate concentration showed a later remarkable decline at 12 h since vasopressin administration. All the 70 patients survived to hospital discharge. In conclusion, low dose of vasopressin administration was associated with great and timely hemodynamic improvement for pediatric patients with vasodilatory shock after cardiac surgery without any significant adverse effects.