The occurrence of an isolated ovarian or pelvic relapse of acute lymphoblastic leukemia (ALL) in complete remission after chemotherapy has rarely been described. We report the case of a 12-year-old girl, treated for ALL, who developed an isolated left ovarian and fallopian tube localization without medullary or blood relapse 4 years after the end of the initial treatment. She presented with an isolated pelvic mass. The diagnosis was established by a CT-guided biopsy. The treatment consisted of a second course of chemotherapy and complementary surgery; a second complete remission was obtained.