As suicide remains a global public health concern, recent work has sought to characterize mechanisms underlying the transition from suicidal ideation to action. Acquired capability for suicide, or fearlessness about death, has been identified as one key factor underlying this transition; however, understanding how this capability emerges remains limited. This study sought to extend previous work on the correlates of fearlessness about death by examining its relationship with painful and provocative events and emotional reactivity. We tested the extent to which trait emotional reactivity and past self-injurious behavior moderated the relationship between assaultive trauma exposure and fearlessness about death in a diverse sample of 273 community adults (aged 18-55, M/SD = 32.77/10.78). A three-way interaction emerged, such that among individuals with heightened emotional reactivity and a history of self-injurious behavior (suicide attempt or non-suicidal self-injury), assaultive trauma was associated with increased fearlessness about death. In contrast, among adults with low emotional reactivity and a history of self-injurious behavior, assaultive trauma was associated with reduced fearlessness about death. Results suggest that emotional reactivity may be a key dispositional factor that influences how trauma exposure and self-injurious behavior impact fearlessness about death.