Studies have reported significant immediate impacts of the COVID-19 pandemic on the social relationships and health care of people living with HIV. This study followed a closed cohort of young people living with HIV over the first year of the COVID-19 pandemic. Participants were men and women (N = 140) age 36 years and younger who were living with HIV and had demonstrated suboptimal adherence to antiretroviral therapy, unsuppressed HIV viral load, or active substance use in a run-in study. The results confirmed that participants continued to experience significant disruptions to their social relationships and health care over the course of the first year of the COVID-19 pandemic. There was evidence for sustained impacts on transportation, housing stability, and food security during the first year of COVID-19. Multivariable models showed that greater pre–COVID-19 social support predicted greater antiretroviral therapy adherence and greater HIV suppression (lower viral load) over the first year of the COVID-19 pandemic. Efforts to plan and prepare people living with HIV for future social crises, including future pandemics, should emphasize building and sustaining social support. [ABSTRACT FROM AUTHOR]