A two-year-old girl with a juvenile granulosa cell tumor (JGCT) and with acutely progressive hydrothorax and ascites is presented. She had precocious pseudopuberty and an elevated level of serum estradiol. Sudden onset of respiratory distress, due to a pleural effusion and severe abdominal distention, led to an emergency laparatomy. Unilateral salpingo-oophorectomy induced a rapidly favorable course. Histological examination showed no evidence of invasion or peritoneal metastasis. This is the first case of JGCT associated with an acute respiratory emergency as a main clinical feature.