Background Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Relapse of ALL occurs in 15%-20% of patients, with 2%-6% occurring exclusively in extramedullary sites. Relapse of ALL in gynecologic organs is extremely rare. Case We present a case of a 12-year-old girl with a history of ALL who was referred to the pediatric gynecology clinic with abnormal uterine bleeding. She was determined to have an extramedullary uterine relapse of her ALL. Summary and Conclusion Abnormal uterine bleeding in the setting of childhood malignancy is a frequent reason for consultation to pediatric and adolescent gynecology services. This bleeding is commonly attributed to thrombocytopenia due to bone marrow suppressive chemotherapeutic agents. However, as shown in this report, abnormal uterine bleeding might be a manifestation of an extramedullary relapse.