The extent, severity, and radiological findings of ovarian growth in infants with genetic syndromes of insulin resistance have not been fully described. We report a rare case of reversible massive ovarian enlargement in a female infant with a congenital insulin resistance syndrome, likely Rabson-Mendenhall syndrome given the less clinically severe course. The patient presented with neonatal diabetes with hyperinsulinemia and hyperglycemia due to congenital insulin resistance. She developed increasing severe bilateral ovarian enlargement which peaked at 4 months of age, followed by gradual decrease in size of the ovaries following treatment with insulin-sensitizing drugs and improved hyperinsulinemia. The ovarian enlargement is postulated to be secondary to the trophic effects of insulin acting in a gonadotropin-independent mechanism. Hyperinsulinemia in congenital insulin resistance can also result in hypertrophy of other organs. Understanding the pathophysiology behind massive ovarian enlargement in the setting of congenital insulin resistance syndromes can help guide appropriate therapy.