Malignant ovarian tumors are responsible for 2-3% of all cases of precocious pseudo-puberty (PP) in girls. The most common forms of ovarian tumors presenting as PP are the granulosa cell tumors (GCT). The clinical and pathological features of granulosa cell tumors that occur frequently in young girls, so-called juvenile granulosa cell tumors (JGCT), differ histologically from those occurring in adults. As a cause of PP in young girls, adult type granulosa cell tumors (AGCT) are extremely rare. We report a 6 year-old girl presenting with early breast development and vaginal bleeding due to a well encapsulated ovarian tumor. Microscopic features of the resected tumor were characteristic of AGCT.