ObjectiveTo conduct a randomized controlled trial assessing the impact of a family-based intervention delivered to Burmese migrant families displaced in Thailand on parenting and family functioning.Participants and proceduresParticipants included 479 Burmese migrant families from 20 communities in Thailand. Families, including 513 caregivers and 479 children aged 7 to 15 years, were randomized to treatment and waitlist control groups. The treatment group received a 12-session family-based intervention delivered to groups of families by lay facilitators. Adapted standardized and locally derived measures were administered before and after the intervention to assess parent-child relationship quality, discipline practices, and family functioning.ResultsCompared with controls, intervention families demonstrated improved quality of parent-child interactions on scales of parental warmth and affection (Effect size (ES) = 0.25 caregivers; 0.26 children, both p < 0.05) and negative relationship quality (ES = -0.37, p < 0.001 caregivers; -0.22 children, p < 0.05). Both children and caregivers also reported an effect on relationship quality based on a locally derived measure (ES = 0.40 caregivers, p < .001; 0.43 children, p < .05). Family functioning was improved, including family cohesion (ES = 0.46 caregivers; 0.36 children; both p < 0.001) and decreased negative interactions (ES = -0.30 caregivers, p < 0.01; -0.24 children, p < 0.05). Family communication also improved according to children only (ES = 0.29, p < 0.01). Caregivers, but not children, reported decreased harsh discipline (ES = -0.39, p < 0.001), and no effects were observed on use of positive discipline strategies. Treatment attendance was high, with participants attending a mean of 9.7 out of 12 sessions.ConclusionThe intervention increased protective aspects of family well-being for migrant children and caregivers in a middle-income country. The strongest effects were on parent-child relationship quality and family functioning, while results were mixed on changes in discipline practices. Results suggest that a behavioral family-based approach implemented by lay providers in community settings is a promising intervention approach for strengthening families in highly stressed contexts.Trial registrationClinicaltrials.gov: NCT01668992