Introduction: Our research was based on the BUS model, which provides guidelines for developing mobile applications for health. This model is supported by theories of behavior change, user-centered design, and social marketing. This study aimed to determine secondary school students’...

Adolescent tobacco use remains a critical public health challenge, requiring innovative early prevention strategies. This study participatively evaluated a medium-fidelity prototype of the No le entres app, designed to prevent tobacco use among adolescents. The prototype was developed based on user-centered design and gamification frameworks, with the aim of ensuring cultural relevance and active user engagement. Qualitative design with content analysis was employed. Four focus groups were conducted in Xalapa, Veracruz: two with health professionals from Medical Specialty Units—Community Mental Health and Addiction Centers (UNEME CECOSAMA), and two with secondary school students. Nineteen professionals and twenty-two adolescents participated. Data were analyzed using MAXQDA 2022, applying both a priori and emergent categories. Professionals valued the app’s innovative approach but recommended improvements in navigation speed, visual design, message clarity, and cultural validation. Adolescents emphasized the need for more engaging features, such as music, rewards, team competitions, and updated graphics. Both groups highlighted the importance of interactivity, personalization, and contextualized content. Findings underscore the value of participatory methods in designing digital health interventions and confirm that involving end users enhances usability and acceptability. The app demonstrates potential for integration into school settings as a preventive tool, with implications for influencing adolescent knowledge, attitudes, and behaviors regarding tobacco use.