Aim.: People released from prison are at higher risk of mortality from potentially preventable causes than their peers in the general population. Because most studies of this phenomenon are reliant on registry data, there is little health and behavioural information available on those at risk, hampering the development of targeted, evidence-based preventive responses. Our aim was to identify modifiable risk and protective factors for external cause and cause-specific mortality after release from prison. Methods.: We undertook a nested case–control study using data from a larger retrospective cohort study of mortality after release from prison in Queensland, Australia between 1994 and 2007. Cases were 286 individuals who had died from external causes (drug overdose, suicide, transport accidents, or violence) matched with 286 controls on sex, Indigenous status, and release date. We extracted data from detention, case-management, and prison medical records. Results.: Factors associated with increased risk of external cause mortality included use of heroin and other opioids in the community [odds ratio (OR) = 2.20, 95% CI 1.41–3.43, p < 0.001], a prescription for antidepressants during the current prison sentence (OR = 1.94, 95% CI 1.02–3.67, p = 0.042), a history of problematic alcohol use in the community (OR = 1.54, 95% CI 1.05–2.26, p = 0.028), and having ever served two or more custodial sentences (OR = 1.51, 95% CI 1.01–2.25, p = 0.045). Being married (OR = 0.45, 95% CI 0.29–0.70, p < 0.001) was protective. Fewer predictors were associated with cause-specific mortality. Conclusions.: We identified several behavioural, psychosocial, and clinical markers associated with mortality from preventable causes in people released from prison. Emerging evidence points to interventions that could be targeted at those at increased risk of external cause mortality. These include treatment and harm reduction programmes (for substance use), improving transitional support programmes and continuity of care (for mental health), diversion and drug reform (for repeat incarceration) and nurturing stable relationships during incarceration. The period of imprisonment and shortly after release provides a unique opportunity to improve the long-term health of ex-prisoners and overcome the disadvantage associated with imprisonment.