In the year following the 2010 Haiti earthquake, local earthquake survivors trained as lay mental health workers implemented a culturally-adapted, psychosocial and trauma-focused group intervention for residents of camps for internally displaced peoples (IDPs). Analysis of evaluation data collected at three Port-au-Prince IDP camps revealed decreased self-reported posttraumatic distress (measured using the Harvard Trauma Questionnaire) associated with participation in this intervention. Improvement occurred across all three PTSD symptom clusters (re-experiencing, avoidance, and hyperarousal). Female participants reported higher baseline distress, were more likely to participate in the intervention, and benefitted more than did men. Results provide initial support for the effectiveness of train-the-trainer interventions utilizing local lay disaster survivors.