BACKGROUND: Workplace burnout can result in negative consequences for clinicians and patients. We assessed burnout prevalence and sources among pediatric hematology/oncology inpatient nurses, ambulatory nurses, physicians (MDs), and advanced practice providers (APPs) by evaluating effects of job demands and involvement in patient safety events (PSEs). METHODS: A cross-sectional survey (Maslach Burnout Inventory) measured emotional exhaustion, depersonalization, and reduced personal accomplishment. The NASA Task Load Index measured mental demand, physical demand, temporal demand, effort, and frustration. Relative weights analyses estimated the unique contributions of tasks and PSEs on burnout. Post-hoc analyses evaluated open-response comments for burnout factors. RESULTS: Burnout prevalence was 33%, 20%, 34% and 33% in inpatient nurses, ambulatory nurses, and MD, and APPs respectively (N=481, response rate 69%). Reduced personal accomplishment was significantly higher in inpatient nurses than MDs & APPs. Job frustration was the most significant predictor of burnout across all four cohorts. Other significant predictors of burnout included temporal demand (nursing groups & MDs) effort (inpatient nurses & MDs) and PSE involvement (ambulatory nurses). Open-response comments identified time constraints, lack of administrator support, insufficient institutional support for self-care, and inadequate staffing and/or turnover as sources of frustration. CONCLUSIONS: All four clinician groups reported substantial levels of burnout, and job demands predicted burnout. The body of knowledge on job stress and workplace burnout supports targeting organizational-level sources, versus individual-level factors, as the most effective prevention and reduction strategy. This study elaborates on this evidence by identifying structural drivers of burnout within a multidisciplinary context of pediatric hematology/oncology clinicians.