Although posttraumatic stress disorder (PTSD) and other psychiatric symptoms are well-established risk factors for suicidal ideation among returning veterans, less attention has been paid to whether the stress of reintegrating into civilian society contributes to suicidal ideation. Utilizing a sample of 232 returning veterans (95% male, mean age = 33.63 years) seeking PTSD treatment, this study tested whether reintegration difficulties contribute to suicidal ideation over and above the influence of PTSD symptoms, depression symptoms, and potential substance misuse. Logistic regressions indicated that reintegration stress had a unique effect on suicidal ideation over and above PTSD and depression symptoms. Reintegration stress interacted with substance misuse to predict suicidal ideation, such that the effect of reintegration stress on suicidal ideation was much larger for those with potential substance misuse. Exploratory analyses also examined which types of reintegration difficulties were associated with suicidal ideation, and found that difficulty maintaining military friendships, difficulty getting along with relatives, difficulty feeling like you belong in civilian society, and difficulty finding meaning/purpose in life were all significantly associated with suicidal ideation, beyond the effects of psychiatric symptoms and potential substance misuse. Findings highlight the importance of addressing reintegration stress for the prevention of suicide among returning veterans. Implications for treatment are discussed.