This study aims to explore the factors that explain the mental sequelae of war-related sexual violence and focuses in particular on the role of stigmatization. Drawing on a large-scale quantitative survey undertaken in the war-affected region of eastern Democratic Republic of the Congo, we analyze how stigmatization mediates the mental health impact of sexual violence on adolescent girls who were victims of rape. Twenty-two secondary schools were randomly selected out of a stratified sample in Bunia, Eastern Congo. In a cross-sectional, population-based survey, 1,305 school-going adolescent girls aged 11-23 completed self-report measures assessing war-related traumatic events, experiences of sexual violence, stigmatization, and mental health symptoms. Of the 1,305 participants, 38.2% (n=499) reported experiences of sexual violence. Victims of sexual violence reported more war-related traumatic events and more stigmatization experiences. Several hierarchical regression analyses examined the mediating impact of stigmatization on the relationship between sexual violence and mental health outcomes, thereby controlling for sociodemographics (age, parental availability, and socioeconomic status) and war-related traumatic exposure. Our findings show that this stigmatization largely explains the mental health impact of sexual violence, in particular, on adolescent girls' reported symptoms of depression (full mediation) and posttraumatic stress (avoidance and total PTSD: full mediation; hyperarousal: partial (40%) mediation). No evidence of mediation by stigmatization was found for symptoms of anxiety and intrusion. Stigmatization plays thus an important role in shaping the mental sequelae of sexual violence, a finding with major consequences for clinical practice.