Complicated grief (CG) is a bereavement-specific syndrome distinct from but commonly comorbid with posttraumatic stress disorder (PTSD). While bereavement is common among military personnel (Simon et al., 2018), there is little research on the impact of CG comorbidity on PTSD treatment outcomes. To evaluate the impact of comorbid CG on PTSD treatment outcomes we analyzed data from a randomized trial comparing prolonged exposure, sertraline, and their combination in veterans with a primary diagnosis of combat-related PTSD (n = 194). Assessment of PTSD, trauma-related guilt, functional impairment, and suicidal ideation and behavior occurred at baseline and weeks 6, 12, and 24 during the 24-week trial. CG was associated with lower PTSD treatment response (odds ratio (OR) = 0.29, 95% confidence interval (CI) [0.12, 0.69], p = 0.005) and remission (OR = 0.28, 95% CI [0.11, 0.71], p = 0.007). Those with CG had greater severity of PTSD (p = 0.005) and trauma-related guilt (<0.001) at baseline and endpoint. In addition, those with CG were more likely to experience suicidal ideation during the study (CG: 35%, 14/40 vs. no CG 15%, 20/130; OR = 3.01, 95% CI [1.29, 7.02], p = 0.011). Comorbid CG is associated with elevated PTSD severity and independently associated with poorer endpoint treatment outcomes in veterans with combat-related PTSD, suggesting that screening and additional intervention for CG may be needed. © 2020 Wiley Periodicals, Inc.