Childhood maltreatment is associated with multiple adverse outcomes in adulthood including poor mental health and violence. We investigated direct and indirect pathways from childhood maltreatment to adult violence perpetration and the explanatory role of psychiatric morbidity. Analyses were based on a population survey of 2,928 young men 21–34 years in Great Britain in 2011, with boost surveys of black and minority ethnic groups and lower social grades. Respondents completed questionnaires measuring psychiatric diagnoses using standardized screening instruments, including antisocial personality disorder (ASPD), drug and alcohol dependence and psychosis. Maltreatment exposures included childhood physical abuse, neglect, witnessing domestic violence and being bullied. Adult violence outcomes included: any violence, violence toward strangers and intimate partners (IPV), victim injury and minor violence. Witnessing domestic violence showed the strongest risk for adult violence (AOR 2.70, 95% CI 2.00, 3.65) through a direct pathway, with psychotic symptoms and ASPD as partial mediators. Childhood physical abuse was associated with IPV (AOR 2.33, 95% CI 1.25, 4.35), mediated by ASPD and alcohol dependence. Neglect was associated with violence toward strangers (AOR 1.73, 95% CI 1.03, 2.91), mediated by ASPD. Prevention of violence in adulthood following childhood physical abuse and neglect requires treatment interventions for associated alcohol dependence, psychosis, and ASPD. However, witnessing family violence in childhood had strongest and direct effects on the pathway to adult violence, with important implications for primary prevention. In this context, prevention strategies should prioritize and focus on early childhood exposure to violence in the family home.