Background. HIV is one of the primary causes of death in Guatemala, and during the period 2005 to 2013, Guatemala exhibited a 95% increase in such deaths. HIV transmission rates are nearly 3 times higher among the indigenous Mayan population than nonindigenous Guatemalans. Guided by the community-based participatory research approach, this article demonstrates the iterative formative research process necessary to develop a deeper and more informed understanding of HIV prevention attitudes and behaviors in the priority population. This project extends preliminary formative research that demonstrated the applicability of the health belief model (HBM) in examining risk, stigma, and barriers and facilitators to condom use and HIV testing. Method. Using an integrated mixed-method design, data were collected from heterosexual adults 18- to 25 years old (N = 250), including 50 in-depth interviews and 200 rapid assessment surveys. Results. HBM concepts of risk and stigma were confirmed. Data also revealed low rates of condom negotiation and high embarrassment in purchasing and discussing condom use. Furthermore, data yielded very low uptake rates and reduced levels of comfort with getting tested. Conclusion. This research informs refinement of a culture-specific intervention prioritizing indigenous Mayans. We highlight how community-based research and engagement enhance community health promotion.