Engaging communities in community-based health research is increasingly being adopted in low- and middle-income countries. The use of community advisory boards is one method of practicing community involvement in health research. To date, few studies provide in-depth accounts of the strategies that CAB members use to practice community engagement. We assessed the perspectives, experiences and practices of the first local CAB in Eswatini, which was implemented as part of the MaxART Early Access to ART for All study. Trained Swazi research (...) assistants conducted two focus group discussions and 13 semi-structured interviews with CAB members who had been part of the MaxART study for at least 2.5 years. Interviews explored CAB composition and recruitment, the activities of CAB members, the mechanisms used to engage with communities and the challenges they faced in their role. The MaxART CAB played an active role in the implementation of the Early Access to Art for All study, and activities mainly focused on: promoting ethical conduct, in particular privacy, consent and confidentiality; communication and education, communicating about the study and educating the community on the benefits of HIV testing and early access to HIV treatment; and liaising between the community and the research team. Strategies for interacting with communities were varied and included attending general community meetings, visiting health facilities and visiting public places such as cattle dipping tanks, buses, bars and churches. Differences in the approach to community engagement between CAB members living in the study areas and those residing outside were identified. The experiences of the first CAB in Eswatini demonstrate that community engagement using CABs is a valuable mechanism for engaging communities in implementation studies. Considerations that could impact CAB functioning include clearly defining the scope of the CAB, addressing issues of CAB independence, the CAB budget, providing emotional support for CAB members, and providing continuous training and capacity building. These issues should be addressed during the early stages of CAB formation in order to optimize functioning. (shrink)