Juvenile granulosa cell tumor of the left ovary occurring in a 21-year-old unmarried women was reported. This is a variety of granulosa cell tumor that is observed almost always in children and has a distinctive appearance. Histological patterns characteristic of this tumor are a relatively large follicles with thick walls and cavities, a disorderly mixture of granulosa and theca cells, a marked luteinization with lipid content, and a more malignant appearance with hyperchromatic and immature nuclei than in the adult forms. The prognosis, however, is said to be better than the latter.