Cushing's syndrome (CS) is common after oral steroid use and has also been reported following topical or inhaled use, but it is extremely uncommon after intranasal administration. This is the case of a 6-year-old child who developed Cushing's syndrome after intranasal application of dexamethasone sodium phosphate for a period of 6 months. Pediatricians and other clinical practitioners should be aware that high-dose and long-term nasal steroid administration may cause iatrogenic Cushing's syndrome characterized by complications of glucocorticoid excess as well as serious and even life-threatening complications of adrenal insufficiency.