The efficacy of evidence-based practices with underprivileged groups and non-Western cultures has been a subject of controversy in the trauma psychology and disaster mental health literature. There has been a debate as to whether evidence based assessments and interventions work equally well for diverse populations. Resolving this controversy has been difficult in part because of the methodological challenges involved in the study of cultural mediation of psychological phenomena. The authors argue that adding qualitative research to the evidence base supporting trauma treatments, as a matter of standard practice, can fill this need. Qualitative research can provide a rigorous research basis for the identification of cultural factors to be accounted for in quantitative outcome studies, as well as a rigorous means of understanding the real-world meaning of quantitative outcome findings. This would address Evidence-based practices (EBP) advocates’ concerns about the unscientific nature of the multicultural literature’s critique, and multiculturalism advocate’s concerns about the lack of contextualism in EBP outcome studies of trauma treatments.