Sertoli-Leydig cell tumors belong to the group of sex-cord stromal tumors of the ovary. They account for less than 0,5% of all ovarian neoplasms. The majority of these tumors are benign, and almost all are localised unilaterally. Herewith, we describe an ovarian Sertoli-Leydig cell tumor in an 11-year-old girl. Serum levels of estradiol and progesterone were mildly elevated, while testosterone and androstendion levels were raised to around three- and sevenfold upper normal limit respectively on presentation. A left salpingo-oophorectomy was performed. Microscopically, the tumor was intermediately differentiated. At 6 months follow-up, there was neither clinical nor sonographical evidence of recurrence, and almost all sex hormone levels had returned to within normal range. Treatment of this pathological entity has to be individualized according to patient age, stage of tumor and degree of differentiation.