The interpersonal theory of suicide posits that individuals who experience suicide ideation will only develop suicidal intent, and subsequently engage in suicidal behavior when they have concomitant fearlessness about death and tolerance for physical pain (i.e., the capability for suicide). The current studies examined the hypothesis that one aspect of the capability for suicide—fearlessness of the pain involved in dying—would amplify the positive association between current suicide ideation and a previous suicide attempt in two samples at high risk for experiencing suicide ideation and suicide attempts. Study 1 examined this relation using self-report methods in a sample of adults entering treatment in a mental health outpatient clinic. Study 2 utilized similar methods in a sample of adults admitted to inpatient psychiatry. Both studies indicated that those individuals who reported suicide ideation were more likely than non-ideators to report having attempted suicide only if they also reported greater fearlessness of the pain involved in dying. The current findings support the theorized role of the capability for suicide in the transition from ideation to attempt and also support assessing the capability for suicide in risk assessment.