This is the case report of a 13-year-old male who developed vasopressor-resistant hypotension after cardiac surgery for endocarditis. As norepinephrine resulted in aggravation of the preexisting ventricular arrhythmia, vasopressin was used to maintain blood pressure. The vasopressin continuous infusion was started at 0.00002 units/kg/min and titrated up to 0.0003 U/kg/min. This low dose led to resolution of hypotension without causing side effects. As the appropriate indication and dose of vasopressin is not established, the cautious use of vasopressin in children is recommended.