Many people who think about suicide do not engage in suicidal behavior. Identifying risk factors implicated in the process of behavioral enaction is crucial for suicide prevention, particularly in high-risk groups such as prisoners. Method: Cross-sectional data were drawn from a nationally representative sample of 17,891 prisoners (79% men) in the United States. We compared prisoners who attempted suicide (attempters; n = 2,496) with those who thought about suicide but never made an attempt (ideators; n = 1,716) on a range of established risk factors. Results: More than half (59%) of participants who experienced suicidal ideation had also attempted suicide. Violent offending, trauma, brain injury, alcohol abuse, and certain mental disorders distinguished attempters from ideators. Conclusion: Our results fit within recent ideation-to-action theories that emphasize the role of a capability for suicide in the transition from thoughts to acts of suicide. Suicide is a global public health concern (Turecki et al., 2019) which disproportionally impacts on the most vulnerable members of society, including people exposed to the criminal justice system (Webb et al., 2011). Specifically, suicide is a leading cause of death in prisoners (Favril, Wittouck, Audenaert, & Vander Laenen, 2019), with rates at least three times higher than in age-equivalent peers outside prison (Fazel, Ramesh, & Hawton, 2017). Prisoners who die by suicide only represent the tip of the iceberg; many more consider or attempt suicide without a fatal outcome. Large-scale studies from Australia