Poor urban children in South Africa are exposed to multiple community traumas, but AIDS-orphaned children are at particular risk for posttraumatic stress. This study examined the hypothesis that social support may moderate the relationship between trauma exposure and posttraumatic stress for this group. Four hundred twenty-five AIDS-orphaned children were interviewed using standardized measures of psychopathology. Compared to participants with low perceived social support, those with high perceived social support demonstrated significantly lower levels of PTSD symptoms after both low and high levels of trauma exposure. This suggests that strong perception of social support from carers, school staff, and friends may lessen deleterious effects of exposure to trauma, and could be a focus of intervention efforts to improve psychological outcomes for AIDS-orphaned children.