ABSTRACT Background: Black sexual minority men (SMM) are disproportionately impacted by HIV and multiple social determinants of health (SDOH), such as housing instability, unemployment, and criminal justice involvement, which pose significant barriers to linkage, engagement, and retention in HIV care. Interventions to address these intersecting factors are resource intensive and logistically challenging, and the best implementation strategies remain unclear. Agent-based models (ABMs) can be used to virtually evaluate candidate interventions and implementation strategies to facilitate more efficient and timely intervention development, and combined with iterative community and public health stakeholder feedback can provide important insights about which intervention strategies and implementation levers would be most effective and efficient in real-world settings. Objective: Building on an existing ABM platform, this proposal will utilize multiple existing local data sources and new data collected through qualitative interviews and focus groups to better understand barriers to linkage, engagement, and retention in HIV care among Black SMM. We will combine methods from epidemiology, agent- based modeling, and implementation science to understand the potential impact of strategies to increase engagement and retention in HIV care on population-level HIV transmission. Methods: We will characterize individual, clinical, and structural level barriers to engagement and retention in care, identify relevant implementation levers, and use this information to simulate (Phase 1) and pilot (Phase 2) implementation strategies to improve re-linkage, engagement, and retention in care among previously diagnosed individuals who are not consistently engaged in care. Significance: A better understanding of where and how to focus efforts to relink out of care individuals and to improve HIV care engagement and retention has the potential to have an important impact on the HIV epidemic and reduce health inequities. Once developed, our methods and models can be adapted to other geographic areas to reflect local prevention priorities and can serve as an example application of implementation science and ABM methods to advance HIV prevention science.