Offenders with antisocial traits are relatively likely to attempt suicide, largely because they are more likely to have high negative emotionality and low constraint. Among 682 male offenders, we tested whether negative emotionality, low constraint, and also substance use problems mediated any relationship between antisocial personality disorder (ASPD) and psychopathy on the one hand, and suicide-related behavior (SRB) and ideation on the other. ASPD and the impulsivity/lifestyle features of psychopathy weakly predicted SRB. High negative emotionality and low constraint (but not substance use) mediated the relation between ASPD and SRB. Impulsivity/lifestyle features of psychopathy retained an independent predictive effect. Self-report psychopathy measures added unique predictive variance to the Psychopathy Checklist-Revised. We discuss implications for suicide risk assessment and prevention.