The article describes the first documented case of successful hepatectomy in a 20-year-old man with focal nodular hyperplasia (FNH) and a constitutional defect of indocyanine green (ICG) excretion, a rare disorder characterized in 1974. Preoperatively, ICG retention at 15 minutes (ICG-R15) was 66.7%, indicating severely impaired clearance. Biochemical parameters of liver function (bilirubin, transaminases, albumin, coagulation profile) were normal, and biopsy of normal liver parenchyma showed no significant changes, thus confirming ICG defect without liver damage. Surgical resection was uncomplicated, with hemodynamic stability, no biochemical liver failure, and histopathology confirmed FNH. The case demonstrates that ICG kinetics alone is unreliable as a sole test of hepatic functional reserve in these patients. A comprehensive preoperative evaluation is essential for a safe surgical procedure.