Over the last 40 years, anatomic reduction with plate stabilization has become the standard in adult patients with diaphyseal fractures of the radius and ulna. When operative fixation has been indicated in skeletally immature patients with these fractures, a variety of techniques have been reported, with intramedullary fixation becoming increasingly accepted. There is currently significant variability in the treatment of adolescents with forearm fractures. The purpose of this study was to investigate the clinical and radiographic outcomes in the adolescent population after intramedullary fixation of both bone forearm fractures. A retrospective review identified 32 patients 12-18 years of age who had undergone intramedullary fixation of both forearm bones in the past 20 years at our institution. Galeazzi, Monteggia, radial head, and distal metaphyseal fractures were excluded. Radiographic evaluation was performed to determine union and postoperative radial bow. Clinical follow-up was carried out for postoperative complications and range of motion of the wrist, forearm, and elbow. The mean age of the patients was 14.1 years. A total of 19 fractures were closed injuries, nine were grade 1, three were grade 2, and one fracture was a grade 3b. Of the patients, 15.6% had limited postoperative range of motion. All patients in the older age group, 15-18 years of age, had a normal range of motion. A decrease in radial bow was not associated with limitation in motion. There was a 98% union rate, and all unions occurred by 7.5 months. Only three major complications occurred, two refractures and one ulnar hardware migration, and subsequent radius nonunion occurred in the one grade 3b injury. Flexible intramedullary nailing of both bone forearm fractures provides reliable bony union and excellent postoperative clinical results in adolescents. Level of evidence, IV.