Ovarian involvement of acute lymphoblastic leukemia (ALL) without relapse in the bone marrow or other extramedullary site is rare. We report a case of ovarian relapse in a 13-year-old girl who was diagnosed with ALL at the age of 11. A complete remission was induced with the Children Cancer Group 1882 protocol for high-risk-groups. After maintenance chemotherapy, the patient remained in relatively good health for the next 4 months. The patient presented with intermittent colicky right lower quadrant pain of 1-day duration. The pelvic ultrasound (US) showed a lobulated mixed echogenic mass in the right ovary, and an exploratory laparotomy was performed. Although uncommon, ovarian recurrence after treatment for ALL should be considered in patients with suggestive symptoms. Regular pelvic US is easy to perform and has no side effects and can help detect ovarian tumors early in ALL survivors.