270 children with suspected distal forearm fractures were randomized in this multi-center, open-label, non-inferiority trial to receive diagnostic imaging with radiography (n=135) or ultrasonography (n=135). The primary outcome of interest was physical function at 4 weeks, as measured by the Pediatric Upper Extremity Short Patient-Reported Outcomes Measurement Information System (PROMIS) scale. Secondary outcomes of interest included satisfaction, pain, time to discharge, frequency of radiographic imaging, missed days of school, and adverse events. No significant differences were observed between the two diagnostic methods for physical function at 1, 4, and 8 weeks; comparable outcomes were observed in the sub-group analysis by diagnostic category and age. Patients who received ultrasonography were discharged earlier, missed fewer days of school, and were more satisfied with treatment. The results of this study suggest a non-inferiority of ultrasonography to radiography for the diagnosis of pediatric distal forearm fractures.