Children born to mothers living with HIV may experience greater risk of poor growth and development outcomes than their HIV-unexposed peers. Few studies have examined the relationship between maternal depression and social support with infant growth and development in the context of HIV. We conducted a prospective cohort study of 2,298 pregnant women living with HIV in Dar es Salaam, Tanzania, assessing antenatal depression (Hopkins Symptoms Checklist-25) and social support (Duke-UNC Functional Social Support Questionnaire) at 12-27 weeks of gestation. At one-year age, infant anthropometry and caregiver-reported infant development were assessed. Generalized estimating equations were used to assess mean differences (MD) and relative risks (RR) for growth and developmental outcomes. Symptoms consistent with maternal antenatal depression had 67% prevalence and were associated with infant wasting (RR 2.61; 95% confidence interval (CI) 1.03-6.65; z = 2.02; p = 0.04), but no other growth or developmental outcomes. Greater maternal social support was not associated with infant growth outcomes. Greater affective support was associated with better cognitive (MD 0.18; CI 0.01-0.35; z = 2.14; p = 0.03) and motor (MD 0.16; CI 0.01-0.31; z = 2.04; p = 0.04) development scores. Greater instrumental support was associated with better cognitive (MD 0.26; CI 0.10-0.42; z = 3.15; p < 0.01), motor (MD 0.17; CI 0.02-0.33; z = 2.22; p = 0.03), and overall (MD 0.19; CI 0.03-0.35; z = 2.35; p = 0.02) development scores. Depressive symptoms were associated with greater risk of wasting, while social support was associated with better infant development scores. Strategies to improve mental health and social support for mothers living with HIV during the antenatal period may benefit infant growth and development.