Complex trauma (CT; for example, childhood abuse) has been associated with significant behavioral health problems (i.e., mental health and substance use disorders) and symptoms that are consistent with complex posttraumatic stress disorder (C-PTSD). CT is prevalent in adult forensic populations, and particularly important for women as they tend to report more adverse consequences of exposure to traumatic stressors and are entering the criminal justice system at a heightened rate compared with men. However, no studies have empirically tested the relationship among CT, C-PTSD, and behavioral health problems with gender among incarcerated adults. The present study examined the relationship between gender and childhood abuse history, C-PTSD symptom severity, and behavioral health problems in 497 incarcerated adults. Findings indicate that women were more likely to report a history of childhood abuse, and more severe C-PTSD symptoms and behavioral health problems than men. Childhood abuse history significantly accounted for the gender difference observed in C-PTSD symptom severity. C-PTSD partially mediated the gender difference in psychiatric morbidity and in risk of hard drug use. Implications for trauma-informed and gender-responsive services and research in the adult criminal justice system are discussed.