OBJECTIVE: Each year, approximately 300,000 pediatric patients are transferred out of emergency departments (EDs). Emergency department transfers may not only provide a higher level of care but also incur increased resource use and cost. Our objective was to identify hospital characteristics and patient demographics and conditions associated with ED transfer as well as the trend of transfers over time. METHODS: This was a retrospective cohort study of pediatric visits to EDs in California using the California Office of Statewide Health Planning and Development ED data set (2005-2018). Hospitals were categorized based on inpatient pediatric capabilities. Patients were characterized by demographics and Clinical Classifications Software diagnostic categories. Regression models were created to analyze likelihood of outcome of transfer compared with admission. RESULTS: Over the 14-year period, there were 38,117,422 pediatric visits to 364 EDs in California with a transfer rate of 1% to 2%. During this time, the overall proportion of pediatric transfers increased, whereas pediatric admissions decreased for all hospital types. Transfers were more likely in general hospitals without licensed pediatric beds (odds ratio [OR], 16.26; 95% confidence interval [CI], 15.87-16.67) and in general hospitals with licensed pediatric beds (OR, 3.54; 95% CI, 3.46-3.62) than in general hospitals with pediatric intensive care unit beds. Mental illness (OR, 61.00; 95% CI, 57.90-63.20), poisoning (OR, 11.78; 95% CI, 11.30-12.30), diseases of the circulatory system (OR, 6.13; 95% CI, 5.84-6.43), diseases of the nervous system (OR, 4.61; 95% CI, 4.46-4.76), and diseases of the blood and blood-forming organs (OR, 3.21; 95% CI, 3.62; 95% CI, 3.45-3.79) had increased odds of transfer. CONCLUSION: Emergency departments in general hospitals without pediatric intensive care units and patients' Clinical Classifications Software category were associated with increased likelihood of transfer. A higher proportion of patients with complex conditions are transferred than those with common conditions. General EDs may benefit from developing transfer processes and protocols for patients with complex medical conditions.