Background <p>Magnetically controlled intramedullary lengthening nails offer a fully internal approach to limb lengthening, avoiding complications associated with external fixators such as pin site infections and soft tissue transfixation. While their use in adults is well-documented, evidence regarding their safety and efficacy in adolescents and young adults remains limited.</p> Methods <p>This retrospective cohort study evaluated the clinical and radiological outcomes of 24 limb lengthening procedures performed in 18 adolescent and young adult patients between 2022 and 2024 using PRECICE^® intramedullary lengthening nails. Patients aged ≤ 18 years with a minimum of 9 months follow-up were included. Lengthening parameters, regenerate morphology, complication rates, and inter-group comparisons were analyzed.</p> Results <p>A total of 24 long bone segments (femur, tibia, and humerus) underwent lengthening in 19 sessions. The mean follow-up period was 18.8 months. The average length gained was 45.7 ± 10.5&#xa0;mm, with a distraction rate of 1.0 ± 0.1&#xa0;mm/day. Complications requiring return to the operating room occurred in 16% of cases, while 5.3% had minor unresolved issues at treatment completion. Radiographic analysis revealed favorable regenerate morphology, and no case showed regenerate insufficiency. Statistical comparison revealed a significantly higher distraction rate in femoral versus tibial lengthenings (<i>p</i> = 0.036).</p> Conclusions <p>Fully internal limb lengthening using magnetically controlled nails is a safe and effective option for adolescents and young adults, with a low rate of complications and high-quality regenerate formation. These findings support broader adoption of internal lengthening in younger patients, particularly in centers with trained teams and appropriate patient selection.</p>