Isolated torsion of the fallopian tube is a rare cause of an acute lower abdominopelvic pain in adolescent females that is difficult to recognize preoperatively. This is a case report of an 11-year-old girl who presented with a right lower quadrant abdominal pain, nausea, and vomiting secondary to isolated torsion of the right fallopian tube 2 days after the onset of her first menses. In this report, the patient's clinical course is discussed with special emphasis on diagnostic imaging and management strategy of adnexal torsion in pubertal and adolescent girls.