Juvenile granulosa cell tumors (JGCTs) are rare tumors, representing 5% of all granulosa cell tumors (GCTs) that occurs in premenarchal girls and young women. Clinical signs in Juvenile granulosa cell tumor after adolescence are menstrual irregularities or amenorrhea in most cases. We describe here a rare case of 23-year-old nulliparous woman with Juvenile granulosa cell tumor, whose only clinical manifestation was abdominal distention due to massive ascites. The patient underwent mass resection with salpingo-oophorectomy. No metastatic implants were noted in the peritoneal cavity, and cytology of ascitic fluid was negative for malignancy. Immunohistochemically, the staining for vascular endothelial growth factor (VEGF) was observed diffusely in the cytoplasm of tumor cells and partly in the endothelial cells, together with marked tumor microvessel density visualized by staining with blood endothelial marker CD34. These results suggest that vascular endothelial growth factor-driven angiogenesis and increased vascular permeability in Juvenile granulosa cell tumor may cause massive ascites production from the tumor itself.