Individuals with serious mental illness and veterans are two populations at elevated risk for suicide; however, research has not examined whether veterans with serious mental illness may be at higher suicide risk than nonveterans with serious mental illness. Additionally, overlapping risk factors for suicide in these populations may account for differences in suicide-related outcomes between these groups. Therefore, the aim of this study was to identify differences in death ideation and suicide ideation among veterans and nonveterans with serious mental illness. We also aimed to explore these effects after adjusting for potentially shared risk factors. We found that veterans with serious mental illness reported death ideation and suicide ideation more than twice as often as nonveterans with serious mental illness. After adjusting for demographic, psychiatric, and theory-driven risk factors, the effect of veteran status on death ideation remained significant, though the effect on suicide ideation was no longer significant. Depressive and psychotic symptoms were significant predictors of death ideation; depressive symptoms and hostility were significant predictors of suicide ideation. Clinicians should particularly monitor death ideation and suicide ideation in veterans with serious mental illness, as well as associated clinical risk factors such as depression, psychotic symptoms, and hostility.