<p>This study examined whether specific dimensions of maternal health literacy mediated the relationship between social vulnerability and maternal caregiving confidence, specifically breastfeeding self-efficacy and maternal beliefs about play, among 168 mothers of newborns in Soweto, South Africa. Social vulnerability was measured using an adapted Social Vulnerability Index, and structural equation modelling was used to assess direct and indirect associations between social vulnerability, maternal health literacy dimensions, and caregiving outcomes. Although most mothers in the sample were classified as socially vulnerable, material deprivation showed no direct association with breastfeeding self-efficacy or maternal beliefs about play. Three dimensions of maternal health literacy-engagement with healthcare providers, ability to find good health information, and ability to understand health information well enough to act-emerged as important pathways shaping mothers’ confidence and caregiving beliefs. The ability to engage with healthcare providers and to find good information partially mediated the effects of social vulnerability, while the ability to understand health information was a strong direct predictor of both outcomes, independent of deprivation. These findings indicate that relational and interpretive literacy skills play a more critical role in shaping maternal confidence than structural disadvantage alone. Strengthening these health literacy skills through targeted interventions may enhance mothers’ confidence in breastfeeding and in supporting healthy play and development in their children, even in contexts of socio-economic vulnerability.</p><p><b>Trial Registration Number</b> PACTR202202747620052.</p>