Although Latino immigrant men experience many health disparities, they are underrepresented in research to understand and address disparities. Community Based Participatory Research (CBPR) has been identified to encourage participant engagement and increase representation in health disparities research. The CBPR conceptual model describes how partnership processes and study design impact participant engagement in research. Using this model, we sought to describe how these domains influenced participant engagement in a pilot randomized controlled trial of brief intervention for unhealthy alcohol use (n = 121) among Latino immigrant men. We conducted interviews with a sample of study participants (n = 25) and reviewed logs maintained by 'promotores'. We identified facilitators of participant engagement, including the relevance of the study topic, alignment with participants' goals to improve their lives, partnerships with study staff that treated participants respectfully and offered access to resources. Further, men reported that the study time and location were convenient and that they appreciated being compensated for their time. Barriers to participant engagement included survey questions that were difficult to understand and competing demands of work responsibilities. Findings suggest that engaging underserved communities requires culturally responsive and community engagement strategies that promote trust. Future studies should further investigate how CBPR partnership processes can inform intervention research.