Aim: Aggression and high-risk behaviours triggered by children in paediatric hospitals are increasing globally. There is a paucity of research describing behavioural emergencies in paediatric acute care settings. Methods: We conducted a 1-year retrospective study of behavioural emergencies that triggered an emergency response team attendance in a quaternary paediatric hospital. Results: In 2018, 218 children triggered 1050 behavioural emergencies, which utilised 386 h of the emergency response team time. Thirty-three (15%) children triggered more than five activations each (range 6–272) and nearly half (16) were children with autism spectrum disorder or intellectual disability. More than 80% of children who triggered an emergency team response also had at least one psychiatric co-morbidity. Conclusions: Behavioural emergencies, by definition, put staff, children or their families at risk. They occur frequently in hospital with some children repeating these behaviours despite allocation of resources and expertise. New approaches to prevention and amelioration are needed.