A majority of individuals seeking asylum in Germany are living in collective housings and thus exposed to a higher risk of contagion during the COVID-19 pandemic. To test feasibility and efficacy of a culture-sensitive approach combining mobile app-based interventions and a face-to-face group intervention to improve knowledge about COVID-19 and promote vaccination readiness among collectively accommodated Arabic-speaking adolescents and young adults. We developed a mobile app that was composed of short video clips to explain the biological basis of COVID-19, demonstrate behavior to prevent transmission, and combat misconceptions and myths about vaccination. Explanations were given in a YouTube-like interview setting by a native Arabic-speaking physician. Elements of gamification (quizzes, rewards for solving test items) were also used. Consecutive videos and quizzes were presented over an intervention period of six weeks, the group intervention was scheduled as an add-on for half of participants in week 6. The manual of the group intervention was designed to provide actual behavior planning on the basis of the health action process approach. Sociodemographic information, mental health status, and knowledge about Covid-19 and available vaccines were assessed with questionnaire-based interviews at baseline and after six weeks. Interpreters assisted with the interviews in all cases. Enrollment in the study proved to be very challenging as among other things, the housing facilities allowed contact with potentially eligible participants only during certain periods because of the pandemic situation. Also due to tightened contact restrictions, the face-to-face group interventions could not be held as planned. A total of 88 participants from 8 collective housing institutions were included in the study. 61 participants completed the full intake interview. Most participants had already been vaccinated at study enrollment (76.5%). They also yet claimed to comply with preventive measures to a very high extent (e.g., "always wearing masks" was indicated by 66% of participants), but practicing behavior that was not considered as effective against Covid-19 transmission was also frequently reported as a preventive measure (e.g., mouth rinsing). On the other hand, factual disease knowledge for COVID-19 was limited. Preoccupation with the information materials presented in the app steeply declined after study enrollment (e.g., 19% of participants watched the videos scheduled for week 3). Only 18 participants could be reached for the follow-up interview. Their COVID-19 disease knowledge did not shown to have increased after the intervention period (p=0.558). The results indicate that vaccine uptake was high and seemed to be depending on organizational determinants for the target group. The current mobile app-based intervention demonstrated low feasibility, which might have been related to various obstacles faced during the delivery: Learning from mobile phone content based on short videos requires a basic understanding of biological and IT-aspects as well as sufficient literacy and a living situation enabling the practical application of the learned behavioral prevention strategies. Therefore, in case of future pandemics, transmission prevention in the specific target group should rely more on structural aspects instead on sophisticated psychological interventions. https://www.drks.de, identifier: DRKS00028825.