BACKGROUND: Internet- and mobile-based mental health interventions have the potential to narrow the treatment gap in ethnic groups. Little evidence exists on the cultural adaptation of such interventions. Cultural adaptation of evidence-based interventions distinguishes between surface and deep structure adaptation. Surface refers to matching materials (e.g., illustrations, language) or methods of treatment delivery to the target population, whereas deep structure adaptation considers cultural concepts of distress (CCD). So far, CCD have only been considered to a limited extent in cultural adaptation of psychological interventions, and there is a lack of well documented adaptation procedures. AIMS: With a cross-disciplinary and mixed-method approach, following a new conceptual framework for cultural adaptation of scalable psychological interventions, this study aimed to develop both surface and deep structure adaptations of an internet- and mobile-based intervention called Hap-pas-Hapi for the treatment of psychological distress among Albanian migrants in Switzerland and Germany. METHODS: A qualitative ethnopsychological study was conducted to examine the target group's CCD. Focus group discussions, an online survey, and individual key informant interviews were utilised to evaluate the original intervention, adaptation drafts and the final adapted intervention. A reporting system was developed to support the decision-making process and to report all adaptations in a transparent and replicable way. RESULTS: The ongoing involvement of target population key informants provided valuable feedback for the development of a more person-centred intervention, which might enhance treatment acceptance, motivation and adherence. DISCUSSION: This study provides empirical and theory-based considerations and suggestions for future implementation that may foster acceptability and effectiveness of culturally adapted evidence-based interventions.