Radial and ulnar fractures are one of the most common fractures in children. When closed reduction of fractures fails, elastic stable intramedullary nail (ESIN) fixation can mostly be used under the guidance of fluoroscopy. In this study, we evaluated the effect of ultrasound (US) as assistance for radial and ulnar fracture reduction and the insertion of ESINs. There were 56 patients with midshaft radial and ulnar fractures included in our hospital from March 2019 to August 2021. After applying the inclusion and exclusion criteria and according to the treatment method, they were divided into the US group (patients treated with US assistance) and the conventional group (C-group, patients treated with fluoroscopy guidance). All patients' clinical data were collected. Operation time, fluoroscopy times, radiation dose, and post-operative complications were analyzed. The elbow function was evaluated using the Mayo Elbow Performance Index. There were 26 patients in the US group and 30 in the C-group. The average operation time was 44.5±19.4 min in the US group and 65.1±16.2 min in the C-group. There were significant differences regarding the surgery time, fluoroscopy time, and radiation dose between the groups (all p = 0.001). The average follow-up time was 13.5±3.1 months. No significant difference was found regarding radial nerve injury, extensor pollicis longus rupture, non-union or delayed union, ulnar nerve injury, or acute compartment syndrome. There was no difference in elbow function at the final follow-up. US guidance can be adopted for the treatment of displaced radial and ulnar fracture reduction and the insertion of ESINs. It can significantly decrease fluoroscopy times, radiation doses, and duration of surgery.