Physical restraint is regularly used in children and adolescent mental health care, often as a reactive behaviour management strategy. Physical restraint has been associated with physical injury, but psychological consequences are poorly understood. The aim of this systematic review was to examine physical restraint of children and adolescents in inpatient mental healthcare services. Healthcare databases were searched to identify English language publications discussing anyone aged ≤18 years who had experienced physical restraint as a mental health inpatient. No date restrictions were applied. Sixteen quantitative studies are included within this review. Most studies are retrospective in nature. Publications were appraised using the Critical Appraisal Skills Programme quality assessment tool. Common characteristics associated with children and adolescents who experience physical restraint include age, gender, diagnosis, and history. Most studies associate physical restraint with the management of aggression. Findings suggest that it may be a combination of patient (intrinsic) and environmental (extrinsic) factors which ultimately lead to children and adolescents experiencing restraint. This review confirms that little is known about children and adolescents’ first-hand experiences of physical restraint. Future research should address children and adolescents’ perceptions and first-hand experiences of physical restraint.