Background <p>Adrenocorticotropic hormone (ACTH)-independent Cushing syndrome is extremely rare in children, with moon face, central obesity, buffalo hump, and hypertension as typical characteristics. We focused on perioperative hemodynamic management because this patient had left ventricular outflow tract obstruction (LVOTO), which is a rare sequela.</p> Case description <p>A 6-month-old boy with ACTH-independent Cushing syndrome and sustained hypertension, with a cortisol level of 49.0&#xa0;µg·dL^− 1, was scheduled to undergo open adrenal tumor resection. Since the preoperative echocardiogram showed left ventricular hypertrophy and LVOTO, preoperative fluid loading was performed over 2 days to optimize fluid volume. For anesthesia induction, the ramp position helped maintain airway patency. Intraoperative and postoperative hemodynamics were generally stable, and hypertension during tumor manipulation was managed by titrating sevoflurane concentration.</p> Conclusions <p>An excessive cortisol level with Cushing syndrome can rarely cause LVOTO in an infant. Not only airway management but also hemodynamic management, including preoperative management, would be essential.</p>