Background: Ovarian tumors in the girl child are sometimes revealed by the development of secondary sexual characteristics. The authors report the case of a five-year-old girl in whom the disease was revealed by early puberty. Case presentation: A five-year-old girl with an enlarged abdomen for about four months. The onset of pain and the sensation of a mass prompted the consultation. The development of secondary sexual characteristics (SSC) noted by the family had not been mentioned. The patient was classified as pubertal stage 2 according to the Tanner classification. An abdominal ultrasound and a CT scan showed a large left ovarian mass, an enlarged uterus for the patient's age and a normal right ovary. The hormonal workup was not contributive. The treatment consisted only of a left salpingo-ovarectomy, without complementary chemotherapy. Anatomic pathological examination of the surgical specimen concluded to a juvenile tumor of the granulosa. The evolution was good with a beginning of regression of the HSC one month after the ovarectomy. Discussion: Granulosa tumors are sometimes secretory cancers, generally with a low potential for malignancy and therefore a very good prognosis. Surgery based on total adnexectomy is the first-line treatment. The large size of the tumor, the presence of ascites and capsular rupture are factors of poor prognosis, hence the importance of early diagnosis. Conclusion: Routine comprehensive physical examination should be de rigueur for abdominal masses in girls, especially in the context of various beliefs that may impede early referral to care.