Purpose: Acute bronchiolitis (AB)-related return visits incur overuse of emergency medicine resources, crowding of emergency departments (EDs), and deterioration of rapport with the guardians. The authors aimed to analyze factors associated with the return visits to the ED.Methods: This study was conducted based on the medical records of 447 children aged 24 months or younger with AB who visited the ED from January 2019 through December 2020. A return visit was defined as an AB-related visit to the ED within 7 days of index visit. According to the return visit, we compared the clinical features. Multivariable logistic regression was conducted to identify independent factors for the return visit.Results: Of the 323 children with AB, 77 (23.8%) made return visits. The returning children showed a younger median age (6 [interquartile range, 2-10] vs. 8 months [3-14]; P < 0.001), a lower mean oxyhemoglobin saturation (92.9 ± 4.3% vs. 97.1 ± 1.8%; P < 0.001), and higher frequencies of congenital heart diseases (22.1% vs. 10.6%; P = 0.009) and bronchopulmonary dysplasia (11.7% vs. 5.7%; P = 0.013), and respiratory syncytial virus infection (57.1% vs. 37.0%; P = 0.002). No other variables, such as the hospitalization rate, differed as per return visits. The factors associated with return visits were respiratory syncytial virus infection (adjusted odds ratio, 9.41; 95% confidence interval, 2.13-41.57), lower oxygen saturation (2.00; 1.64-2.43), and age younger than 3 months (1.25; 1.07-1.24).Conclusion: AB-related return visits may be associated with age younger than 3 months, lower oxygen saturation, and respiratory syncytial virus infection.