Background Critical public health measures implemented to mitigate the spread of the novel coronavirus disease (COVID-19) pandemic have disrupted health research worldwide, including HIV prevention research. While general guidance has been issued for the responsible conduct of research in these challenging circumstances, the contours of the dueling COVID-19 and HIV/AIDS pandemics raise some critical ethical issues for HIV prevention research. In this paper, we use the recently updated HIV Prevention Trials Network (HPTN) Ethics Guidance Document (EGD) to situate and analyze key ethical challenges related to the conduct of HIV prevention research during the COVID-19 pandemic as well as identify potential areas for refinement of the guidance document based on this unprecedented state of affairs. Main body Necessary actions taken for HIV prevention research studies due to the COVID-19 pandemic involve an array of ethical issues including those related to: (1) risk mitigation; (2) behavior change; (3) compounding vulnerability; (4) community engagement; (5) trial reopening; and 6) shifting research priorities. Conclusions In the context of the dueling HIV and COVID-19 global pandemics, research teams and sponsors must be nimble in responding to the rapidly changing environment by being sensitive to the associated ethical issues. The HTPN EGD provides a rich set of tools to help identify, analyze and address many of these issues. At the same time, future refinements of the HPTN EGD and other research ethics guidance could be strengthened by providing explicit advice regarding the ethical issues associated with disrupted research and the reopening of studies. In addition, additional consideration should be given to appropriately balancing domains of risk (e.g., physical versus social), addressing the vulnerability of research staff and community partners, and responding to un-anticipatable ancillary care needs of participants and communities. Appropriately addressing these issues will necessitate conceptual work, which would benefit from the careful documentation of the actual ethical issues encountered in research, the strategies implemented to overcome them, and their success in doing so. Throughout all of these efforts, it is critical to remember that the HIV pandemic not be forgotten in the rush to deal with the COVID-19 pandemic.