BackgroundDiagnostic errors, reframed as missed opportunities for improving diagnosis (MOIDs), are poorly understood in the paediatric emergency department (ED) setting. We investigated the clinical experience, harm and contributing factors related to MOIDs reported by physicians working in paediatric EDs.MethodsWe developed a web-based survey in which physicians participating in the international Paediatric Emergency Research Network representing five out of six WHO regions, described examples of MOIDs involving their own or a colleague’s patients. Respondents provided case summaries and answered questions regarding harm and factors contributing to the event.ResultsOf 1594 physicians surveyed, 412 (25.8%) responded (mean age=43 years (SD=9.2), 42.0% female, mean years in practice=12 (SD=9.0)). Patient presentations involving MOIDs had common undifferentiated symptoms at initial presentation, including abdominal pain (21.1%), fever (17.2%) and vomiting (16.5%). Patients were discharged from the ED with commonly reported diagnoses, including acute gastroenteritis (16.7%), viral syndrome (10.2%) and constipation (7.0%). Most reported MOIDs (65%) were detected on ED return visits (46% within 24 hours and 76% within 72 hours). The most common reported MOID was appendicitis (11.4%), followed by brain tumour (4.4%), meningitis (4.4%) and non-accidental trauma (4.1%). More than half (59.1%) of the reported MOIDs involved the patient/parent–provider encounter (eg, misinterpreted/ignored history or an incomplete/inadequate physical examination). Types of MOIDs and contributing factors did not differ significantly between countries. More than half of patients had either moderate (48.7%) or major (10%) harm due to the MOID.ConclusionsAn international cohort of paediatric ED physicians reported several MOIDs, often in children who presented to the ED with common undifferentiated symptoms. Many of these were related to patient/parent–provider interaction factors such as suboptimal history and physical examination. Physicians’ personal experiences offer an underexplored source for investigating and mitigating diagnostic errors in the paediatric ED.