Background Worldwide, over one billion children and adolescents live in war-affected settings. At present, only limited research has investigated linkages between disrupted social ecology and adverse mental health outcomes among war-affected youth. In this study, we examine three community-level characteristics - social disorder and collective efficacy within the community, as reported by caregivers, and perceived stigma as reported by youth - in relation to externalizing behaviors and internalizing symptoms among male and female former child soldiers in postconflict Sierra Leone. Methods A total of 243 former child soldiers (30% female, mean age at baseline: 16.6 years) and their primary caregivers participated in interviews in 2004 and 2008, as part of a larger prospective cohort study of war-affected youth in Sierra Leone. Two-point growth models were estimated to examine the relationship between community-level characteristics and externalizing and internalizing outcomes across the time points. Results Both social disorder within the community, reported by caregivers, and perceived stigma, reported by youth, positively covaried with youths' externalizing and internalizing scores - indicating that higher levels of each at baseline and follow-up were associated with higher levels of mental health problems at both time points (p .05). Conclusions This study offers a rare glimpse into the role that the postconflict social context plays in shaping the mental health among former child soldiers. Results indicate that both social disorder and perceived stigma within the community demonstrate an important relationship to externalizing and internalizing problems among adolescent ex-combatants. Moreover, these relationships persisted over a 4-year period of follow-up. These results underscore the importance of the postconflict social environment and the need to develop postconflict interventions that address community-level processes in addition to the needs of families and individuals. © 2013 The Authors. Journal of Child Psychology and Psychiatry © 2013 Association for Child and Adolescent Mental Health.