Women and child with HIV/AIDS deserve protection as included in the third goal of SDGs. This qualitative study with phenomenological approach aimed to study structured Peer Education in social capital-based Prevention of Motherto-Child Transmission or PMTCT in Surakarta Indonesia. Units of analysis were mothers either infected or not with HIV, Health Service, AIDS Coping Commission and its workgroup, Solo Plus Peer Suport Group or PSG, NGO and PMTCT service in Surakarta. Informants were selected with purposive sampling technique, data collection with observation, in-depth interview, and documentation, and data validation with method and data source triangulations. Data of informants' activity and experience was analyzed using interpretative phenomenology with social capital theory. Result showed that mothers either infected or not with HIV become targeted group or peer educators in structured PE for PMTCT. Peer educators recruited peer promoter, trained, and educated their peers, conducted socialization, communication, information, education, treatment, reaching, and facilitation based on norm, trust, and social network. Besides being included in PSG's activities, structured PE was conducted in social and religion activities. Strong social network and link to PMTCT stakeholders become a bridge in and between peer educators and targeted group in PMTCT service, so that HIV/AIDS case in mother and children can be controlled.