Background: It is often difficult for the pediatric patient to cooperate or to remain immobile during MR scans. Therefore, sedation is usually needed for children. Purpose: To evaluate the incidence and contributing factors of unanticipated intubation during sedation for MRI scan in children.Study Type: Retrospective observational study. Population/Subjects: In all, 1165 charts were reviewed retrospectively of patients who had been sedated by anesthesiologists at a single institution from May 2015 to June 2016. Assessment: Patient's demographics, the region of the MRI scan, total amount of medication, duration of sedation, and any adverse event during MRI were assessed. The adverse events during sedation including airway obstruction, apnea, desaturation, bradycardia, and hypotension were also assessed. Statistical Tests: Risk factors of unplanned intubation during MRI sedation were identified by univariate and multivariate analysis. Firth's exact logistic regression was used for univariate and multivariate analysis. According to the results from multiple logistic regression, a nomogram was developed to predict the risk. Results: A total of 1165 children aged 7 days to 18 years with sedation used during an MRI scan during the study period showed an incidence of unexpected intubation as~2% (n = 23, 95% confidence interval [CI]; 0.0123, 0.0295). Multivariate logistic regression revealed the following risk factors of unplanned intubation: American Society of Anesthesiologists (ASA) class III patients (odds ratio [OR] 1.212, P < 0.001), premature birth (OR 2.317, P < 0.001), and the presence of gastroesophageal reflux disease (GERD) (OR 1.474, P < 0.001) or congenital heart disease (OR 1.118, P < 0.001). Data Conclusion: This study identified risk factors of unplanned intubation as follows: ASA class III patients, premature birth, and the presence of GERD or congenital heart disease. The physician should screen risk factors of unexpected intubation and maintain adequate sedation during MRI scans in pediatric patients. Level of Evidence 3.