Purpose: While a number of studies have investigated risk factors and comorbidities of ICD-11 post-traumatic stress disorder (PTSD) and complex PTSD (CPTSD) in various trauma exposed samples, few studies have been conducted in military samples. Existing studies with military samples have included rather small samples. The aim of the present study was to identify risk factors and comorbidities of ICD-11 PTSD and CPTSD in a large sample of previously deployed, treatment-seeking soldiers and veterans. Methods: Previously deployed, treatment-seeking Danish soldiers and veterans (N = 599), recruited from the Military Psychology Department of the Danish Defense, completed the International Trauma Questionnaire (ITQ), as well as questionnaires of common mental health difficulties, trauma exposure, functioning and demographics. Multivariate multinomial logistic regression analysis explored differences in self-reported exposure to adversity and health outcomes between those meeting ICD-11 criteria for probable PTSD, CPTSD and no trauma disorder. Results: A total of 13.0% met probable ICD-11 criteria for PTSD and 31.4% for CPTSD. Risk factors for CPTSD (compared to those with no trauma disorder) included exposure to warfare or combat, longer duration since the traumatic event and being single. Those with CPTSD were more likely than those with PTSD or no trauma disorder to endorse symptoms of depression, anxiety, stress, use of psychotropic medication, and suicide attempts. Conclusion: CPTSD is a more common and debilitating condition compared to PTSD in treatment-seeking soldiers and veterans. Further research should focus on testing existing and novel interventions for CPTSD in the military.