HIV stigma remains a barrier to good health and understanding how social support may reduce the negative impact of stigma on health may help with designing stigma interventions. This study aims to understand how different types of social support may moderate or change the nature of the relationship between stigma and mental health. We recruited 327 participants to complete the People Living with HIV Stigma Index at baseline (t1) between August 2018 and September 2019 and at follow-up (t2) between February 2021 and October 2021. Separate moderation models were created with different types of social support (emotional/informational, tangible, affectionate, positive social interaction) as moderators, baseline stigma (internalized, enacted, anticipated) as the antecedent, and mental health (t2) as the outcome. Emotional/informational support was a significant moderator for the relationship between enacted (b = -2.12, 95% CI: -3.73, -0.51), internalized (b = -1.72, 95% CI: -3.24, -0.20), and anticipated (b = -2.59, 95% CI: -4.59, -0.60) stigma at t1 and mental health at t2. Tangible support was a significant moderator for internalized stigma (b = -1.54, 95% CI: -2.74, -0.35). Lastly, positive social interaction was a significant moderator for internalized (b = -1.38, 95% CI: -2.71, -0.04) and anticipated stigma (b = -2.14, 95% CI: -3.93, -0.36). In general, the relationship between social support and better mental health was stronger for participants with low stigma. Intervention strategies aimed at both stigma reduction and boosting social supports with different functions may be important for improving the mental health of people living with HIV.