Black communities in Canada are disproportionately affected by HIV, comprising 24.6% of new cases despite representing only 4.3% of the population. Systemic barriers such as stigma, racial bias, and inadequate access to culturally responsive health services contribute to this disparity. This study engages Black community members and HIV service providers to inform the design and development of a culturally responsive mHealth app for HIV prevention. Guided by community-based research and user-centered design principles, focus group discussions explored preferences for content, functionality, and design of an HIV prevention app. Data collected from focus groups identified five overarching themes: (1) general health concerns, (2) cultural responsiveness, (3) HIV prevention needs, (4) mHealth application preferences, and (5) culturally responsive information needs. Participants emphasized the importance of addressing stigma, providing multilingual options, and ensuring privacy and security. Preferences for app features included geolocation for testing centers, interactive risk assessments, and engaging educational content. The study highlights the critical need for integrating cultural relevance, user-centered design, and robust privacy measures into mHealth apps.