BackgroundResearch suggests that motor difficulties may be closely associated with severe emotional and behavioural problems in children. However, there is limited research on the role of motor function in young adults who offend. AimsTo assess motor skills, balance, and primary reflex persistence in young people who offend, and to examine the relative association of different motor factors with self-reported levels of aggression. MethodsWe recruited three groups of males (14–18 years); young people serving custodial sentences (n = 33) in a youth justice centre, and an IQ-matched comparison group (n = 36) and an average-IQ comparison group (n = 38) of non-offenders. All completed a standardised test of motor skills, clinical assessment protocols for balance and primary reflex persistence, and a standardised self-report behavioural rating scale. ResultsThe youth justice group showed significantly lower abilities in some motor skills and balance and significantly higher levels of primary reflex persistence and aggression than both comparison groups. In a multiple regression model, only manual dexterity (p = .032) and primary reflex persistence (p = .002) were significant predictors of aggression. ConclusionsA broad range of motor difficulties are likely to occur in young people who offend. We discuss the implications of motor difficulties for approaches to rehabilitation of persistent offenders.