BackgroundDelirium is one of the most common complications in critically ill children. Once delirium occurs, it will cause physical and psychological distress in children and increase the length of their ICU stay and hospitalization costs. Understanding the risk factors for delirium in critically ill children can help develop targeted nursing interventions to reduce the incidence of delirium.Aims and ObjectivesTo investigate the incidence and the risk factors of delirium in the paediatric intensive care unit (PICU).DesignProspective observational study.MethodsWe performed a prospective observational study in critically ill patients in the PICU between February and July 2020. Delirium was diagnosed by the Cornell Assessment of Paediatric Delirium (CAPD) and the Richmond Agitation Sedation Scale and analysed via univariate analysis and multivariate logistic regression to determine the independent risk factors of delirium in critically ill children.ResultsThe study enrolled 315 patients ranging in age from 1–202 (65.3–54.3) months, with 56.2% (n = 177) being male. The incidence of delirium was 29.2% (n = 92) according to CAPD criteria. Among them, 33 cases (35.9%) were of hyperactive delirium, 16 cases (17.4%) were of hypoactive delirium, and 43 cases (46.7%) were of mixed delirium. By using stepwise logistic regression, the independent risk factors of delirium included mechanical ventilation (odds ratio [OR], 11.470; 95% confidence interval [CI], 4.283–30.721), nervous system disease (OR, 5.596; 95%CI, 2.445 to 12.809), developmental delay (OR, 5.157; 95% CI, 1.990–13.363), benzodiazepine (OR, 3.359; 95% CI 1.278–8.832), number of catheters (OR, 1.918; 95% CI, 1.425 to 2.582), and age (OR, 0.985; 95% confidence interval CI, 0.976–0.993).ConclusionsDelirium is a common complication in the PICU. The independent risk factors include mechanical ventilation, nervous system disease, developmental delay, benzodiazepines, higher number of catheters, and younger age. This study may help develop intervention strategies to reduce the incidence of delirium in critically ill children by targeting modifiable risk factors.Relevance to Clinical PracticeRecommendations for practice include paying attention to high‐risk children in the ICU who are prone to delirium, removing influencing factors as soon as possible, and providing targeted nursing interventions.