BACKGROUND: Suicidal ideation (SI) is a serious issue affecting U.S. veterans, and those with posttraumatic stress disorder (PTSD) are at an especially high risk of SI. Guilt has been associated with both PTSD and SI and may therefore be an important link between these constructs. METHODS: The present study compared models of trauma-related guilt and used path analysis to examine the direct and indirect effects of PTSD and trauma-related guilt on SI among a sample of 988 veterans receiving outpatient PTSD treatment at a Veterans Affairs (VA) specialty clinic. RESULTS: Results showed that a model of trauma-related guilt including guilt-cognitions and global guilt (but not distress) provided the best model fit for the data. PTSD and trauma-related guilt had direct effects on SI, and PTSD exhibited indirect effects on SI via trauma-related guilt. LIMITATIONS: The use of cross-sectional data limits the ability to make causal inferences. A treatment-seeking sample composed primarily of Vietnam veterans limits generalizability to other populations. CONCLUSIONS: Trauma-related guilt, particularly guilt cognitions, may be an effective point of intervention to help reduce SI among veterans with PTSD. This is an important area of inquiry, and suggestions for future research are discussed.