Purpose: Displaced children’s forearms fractures are commonly treated surgically with Kirschner Wires or Elastic Stable Intramedullary Nails. The osteosynthesis system “Minimally Invasive Reduction and Osteosynthesis System” might be beneficial in the treatment of these fractures due to being minimally invasive while achieving fracture stability. In this exploratory prospective randomized controlled longitudinal study, we compared Minimally Invasive Reduction and Osteosynthesis System to Kirschner Wires and Elastic Stable Intramedullary Nails osteosynthesis. Methods: Twenty children were included consecutively to treatment with either conventional surgery (5 Kirschner Wires/5 Elastic Stable Intramedullary Nails) or Minimally Invasive Reduction and Osteosynthesis System (10). Evaluation of radiographic alignment and clinically of range of motion, pain status, grip strength, level of physical activity and scar size were compared after 3 months and after 5 years. Results: Surgical parameters of the duration of insertion-and removal-surgery, the need for postoperative casting and scar size were significantly better for Minimally Invasive Reduction and Osteosynthesis System. All osteosynthesis systems maintained radiographically fracture alignment at three months and 5 years follow-up. Clinical status regarding pain, grip strength difference, and return to recreational activities were not significantly different. The complication rates were nonsignificant, but MIROS had moderate severe complications of refractures, while mild complications occurred when operated on with Kirschner Wires/Elastic Stable Intramedullary Nails. Our study was sufficiently powered at 3 months, but the comparisons are suggestive at 5 years. Conclusion: In conclusion, Minimally Invasive Reduction and Osteosynthesis System is not significantly different to other surgical methods in radiological outcomes for forearm fractures in children. Minimally Invasive Reduction and Osteosynthesis System has the clinical benefit of omitting casting after surgery, obtaining reduced scar size, and shorter insertion and removal time without general anesthesia. However, moderately severe complications occurred. Level of evidence: Level II—a prospective comparative study.