Few studies have explored the relationship between early infant diagnosis(EID) of HIV and mothers’engagement in care under Option B+. Weconducted in-depth interviews with 20 women who initiatedantiretroviral therapy (ART) under Option B+ in rural South Africa toexplore the interactions between EID and maternal care engagement.Drawing on practice theory, we identified themes relating to Option B+care engagement and EID. Women’s practice of engagement with HIVcare shaped their decision-making around EID. Mothers who disengagedfrom care during pregnancy were less inclined to utilise EID as theylacked information about its availability and benefits. For some mothers,tensions between wanting to breastfeed and perceptions that it couldfacilitate transmission led to repeated utilisation of EID as reassurancethat the child remained negative. Some mothers used their child’snegative result as a proxy for their status, subsequently disengagingfrom care. For some participants, an HIV diagnosis of their infant and thesubsequent double burden of treatment visits for themselves and theirinfant, contributed to their disengagement. Women’s care-seekingpractices for themselves and their infants work in a symbiotic ecosystemand should be viewed interdependently to tailor interventions toimprove EID uptake and Option B+ care engagement.