Uterine leiomyomas are rare in the pediatric population with less than 20 cases in adolescences reported in the literature. Furthermore, these masses represent a common presentation of gynecologic tumors with increasing age. We report a case of a 14-year-old female who presented with abdominal pain and increasing abdominal girth. Workup with ultrasound, CT and MRI demonstrated a large pelvic mass. Complete resection by median laparotomy was performed. The mass weighed 5,596 g and was 29.5 cm × 27 cm × 19 cm; the pathological examination confirmed the hypothesis of leiomyoma. The patient remained asymptomatic at 3 months follow up.