Key to the success of a HIV combination prevention strategy, including galvanizing the current push to roll out universal test and treat (UTT), is the involvement and buy-in of the populations that the strategy aims to reach. Drawing on the experiences of engaging with 21 communities in Zambia and South Africa in the design and implementation of a community-randomized study of combination HIV prevention including UTT, this paper reflects on the commitment to, approaches for and benefits of involving communities. Key lessons learnt include that all communities require continuous community engagement (CE) and engagement needs to be adapted to diverse local contexts. Intrinsic goals of CE, such as building trusting relationships between study stakeholders, are necessary precursors to instrumental goals which strengthen the research quality. Engaging the community for combination prevention requires that CE successfully bridges science and real life, paying attention to influences in the wider social landscape.