Purpose: To investigate the prevalence of Traumatic Brain Injury (TBI) among young incarcerated males and determine the extent of deficits in behavioural regulation, aggression, hopelessness and perceived social support, compared to a control group of non-incarcerated males. Methods: Sixty-two young offenders and fifty-eight university-based, gender-matched controls agreed to take part. We collected information on criminal history, risk taking behaviour, drug and alcohol abuse and mental illness. In addition, we employed measures of Brain Injury, Hopelessness, Behavioural Regulation, Aggression and Perceived Social Support. Results: Just over 87% (n=54) of offenders exhibited some level of TBI with over 31% (n=17) reporting 6 or more injuries. Offenders with TBI exhibited poorer behavioural control (p <.001; M=66.01 Vs. M=51.33; 95% CI -19.08 to -11.76), higher levels of aggression (p <.001; M=101.19 Vs. M=69.39; 95% CI -38.31 to -27.17) and higher levels of hopelessness (p<.001; M=5.65 Vs. M=2.55) when compared to controls with TBI. Severity of TBI correlated positively with behavioural regulation, aggression and hopelessness. Conclusions: Greater recognition of the presence and consequences of TBI within the custodial estate is necessary if the needs of young offenders are to be adequately met. Young offenders with TBI experience heightened vulnerability and need rehabilitative input to support their time in prison and on their return to society.