There is widespread recognition of the cultural and linguistic appropriateness of promotoras de salud (a Spanish term for community health workers) in health education and outreach among Hispanic communities. Yet there are significant gaps in the literature regarding the preparation, implementation and evaluation of promotoras’ engagement in research. To address this gap, we examine promotoras’ research-related training, roles, responsibilities, and contributions in a community-based participatory research project involving a multi-site randomized controlled trial of a physical activity intervention for Mexican-origin women in Texas and South Carolina. We identify both benefits and challenges associated with promotoras’ engagement as community researchers; examine variations and differences in promotora roles and responsibilities related to the research contexts, sites, settings, and individual characteristics; and discuss implications for research and practice.