Poor psychosocial well-being, including depression, anxiety, low self-esteem, and high anticipated stigma, complicates young South Africans' engagement with HIV care. During the COVID-19 pandemic, the psychosocial well-being of young South Africans with HIV may have been impacted by changing levels of social support. This analysis sought to examine whether social support mediates the relationship between the pandemic and psychosocial well-being in young South Africans with HIV. This secondary analysis compared baseline data from two cohorts of young people ages 18-24 who tested HIV positive either before or during South Africa's COVID-19 State of Disaster. Baseline sociodemographic, social support-related, and psychosocial data were analyzed using linear regression and mediation analyses. We found that self-esteem was higher (χ