We report a 9-month-old male Latino infant with congenital nephrogenic diabetes insipidus (NDI) who presented with hypernatremic dehydration aggravated by severe gastroenteritis. Initially, the infant was managed with intravenous fluids followed by standard 20 cal/ounce formula and pharmacological therapy, resulting in normalization of his serum sodium level. While hydrochlorothiazide therapy alone or in combination with prostaglandin inhibitors or amiloride has been successful in children and adolescents, this is the first report of the successful use of hydrochlorothiazide and amiloride in an infant with congenital NDI.