Purpose: Faith-based organizations may be effective in addressing HIV-related disparities, but few interventions have been implemented across diverse churches. The Facilitating Awareness to Increase Testing for HIV (FAITH) intervention harnessed peer leadership to decrease HIV stigma and promote HIV testing in African American and Latino congregations. A pilot study found more consistent effects among Latino congregations. This process evaluation evaluates implementation of FAITH to better understand the pilot study's findings. Methods: Data sources included HIV education and peer leader workshop evaluation forms, participant views of the community's perspective of HIV, and peer leader follow-up interviews. Data were triangulated with systematic observation notes and analyzed using process-related themes of recruitment, reach, context, implementation, dose-delivered, and fidelity. Results: At the Latino churches (compared to the African American church), facilitators spent more time addressing community-based misconceptions about HIV. The peer leader model was well received, especially among Latino participants, and most said that after the workshop they felt comfortable speaking with others about HIV-related topics. Latino peer leaders reported speaking with up to 20 people within their social networks (particularly with family members); African Americans reported up to 4. Implementation challenges at the African American church may have contributed to the limited intervention effects. Nevertheless, we found the peer motivator model feasible and acceptable across diverse faith settings. Conclusion: Peer-based models within faith settings are promising for addressing HIV. However, differences among groups in HIV knowledge, social network characteristics and norms, and church preferences may influence overall effectiveness.