Background: Children frequently present to the emergency department (ED) with forearm injuries and often have x-rays to determine if there is a fracture. Bedside ultrasound, also known as point-of-care ultrasound (POCUS), is an alternative diagnostic test used to rapidly diagnose a fracture at the time of examination, without exposing children to ionising radiation. Prospective studies have demonstrated high agreement between POCUS and x-ray findings. However, whether the initial imaging modality affects the patient’s medium-term physical function is unknown. Methods: This is a multicentre, open-label, non-inferiority randomised controlled trial conducted in Australian EDs. Recruitment will continue until 112 children with distal forearm injuries (including 48 buckle fractures) per trial arm have achieved the primary outcome measure. Patients aged 5–15 years presenting with an isolated, acute, clinically non-angulated, distal forearm injury with suspected fracture will have their initial diagnostic approach randomised to either POCUS, performed by a credentialled practitioner, or x-ray imaging. If a cortical breach fracture is identified on POCUS, the patient will receive x-rays and have usual care. If a buckle fracture is identified, the patient will have their forearm placed in a splint and be discharged home. Patients will be followed up at 1, 4 and 8 weeks. The primary outcome is upper limb physical function at 4 weeks, as determined by the Pediatric Upper Extremity Short Patient-Reported Outcomes Measurement Information System (PROMIS) tool. Secondary outcomes include healthcare costs, satisfaction, pain, complications, rates of imaging, ED length of stay and diagnostic accuracy. Discussion: If POCUS is non-inferior to x-ray in terms of patient’s medium-term physical function, it may have an effect on overall health care resource use, including the number of x-ray performed and earlier ED discharge. Although prospective studies have confirmed the accuracy of POCUS, this will be the first RCT to assess non-inferiority of functional outcomes of POCUS to diagnose non-angulated paediatric distal forearm injuries, compared to x-ray. POCUS may be of particular importance in settings where access to x-ray imaging can be limited either during or after-hours, as it can aid the triaging and management of patients. Trial registration: Prospectively registered with the ANZCTR on 29 May 2020 (ACTRN12620000637943).