Description: Objective and design We conducted a systematic review and meta-analysis to evaluate the incidence of adverse events in the emergency department (ED) during procedural sedation in the paediatric population. Randomised controlled trials and observational studies from the past 10 years were included. We adhere to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Setting ED. Participants Children. Interventions Procedural sedation. Outcomes Adverse events like vomiting, agitation, hypoxia and apnoea. Meta-analysis was performed with random-effects model and reported as incidence rates with 95% CIs. Results A total of 1177 studies were retrieved for screening and 258 were selected for full-text review. 41 studies reporting on 13 883 procedural sedations in 13 876 children (≤18 years) were included. The most common adverse events (all reported per 1000 sedations) were: vomiting 55.5 (CI 45.2 to 65.8), agitation 17.9 (CI 12.2 to 23.7), hypoxia 14.8 (CI 10.2 to 19.3) and apnoea 7.1 (CI 3.2 to 11.0). The need to intervene with either bag valve mask, oral airway or positive pressure ventilation occurred in 5.0 per 1000 sedations (CI 2.3 to 7.6). The incidences of severe respiratory events were: 34 cases of laryngospasm among 8687 sedations (2.9 per 1000 sedations, CI 1.1 to 4.7; absolute rate 3.9 per 1000 sedations), 4 intubations among 9136 sedations and 0 cases of aspiration among 3326 sedations. 33 of the 34 cases of laryngospasm occurred in patients who received ketamine. Conclusions Serious adverse respiratory events are very rare in paediatric procedural sedation in the ED. Emesis and agitation are the most frequent adverse events. Hypoxia, a late indicator of respiratory depression, occurs in 1.5% of sedations. Laryngospasm, though rare, happens most frequently with ketamine. The results of this study provide quantitative risk estimates to facilitate shared decision-making, risk communication, informed consent and resource allocation in children undergoing procedural sedation in the ED.