There has been a recent global increase in the number of young people experiencing mental health challenges in both child and adolescent mental health settings and acute paediatric settings. In many of these settings, restrictive practices are used to manage behaviours that challenge, such as aggression and violence. However, little is known about staff's experiences with responding to behaviours that challenge in these settings. A qualitative descriptive design was adopted, with participants engaging in 1:1 interviews or focus groups in Ireland, Finland, Germany, and Bulgaria. Data were analysed using reflexive thematic analysis. Four themes were identified: (1) the importance of establishing a safe, therapeutic environment, (2) identified antecedents to behaviours that challenge, (3) how staff respond to behaviours that challenge, and (4) the needs of staff when maintaining a safe, therapeutic environment. Consideration needs to be given to the environments where young people are cared for, with an emphasis placed on safe, comfortable, therapeutic spaces to reduce behaviours that challenge. Staff should be better trained in trauma-informed practice, and both staff and service users should be provided with opportunities to de-brief following episodes of restrictive practices, with a focus on enhancing and maintaining therapeutic relationships.