Background The Post Natal Club (PNC) model assures comprehensive care, including HIV and Maternal and Child Health care, for postpartum women living with HIV and their infants during an 18-month postnatal period. The PNC model was launched in 2016 in Town Two Clinic, a primary health care facility in Khayelitsha, South Africa. This qualitative research study aims to understand how participation in PNCs affected knowledge transmission, peer support, behaviour change and satisfaction with the care provided. Methods We conducted ten in-depth interviews; three focus group discussions and participant observation with PNC members, health-care workers and key informants selected through purposive sampling. Seventeen PNC members between 21 and 38 years old, three key informants and seven staff working in PNC participated in the research. All participants were female, except for one of the three key informants who was male. Data was collected until saturation. The data analysis was performed in an inductive way and involved an iterative process, using Nvivo11 software. Results PNC members acquired knowledge on HIV, ART, adherence, infant feeding, healthy eating habits, follow up tests and treatment for exposed infants. Participants believed that PNC created strong relationships among members and offered an environment conducive to sharing experience and advice. Most interviewees stated that participating in PNC facilitated disclosure of their HIV status, enhanced support network and provided role models. PNC members said that they adapted their behaviour based on advice received in PNCs related to infant feeding, ART adherence, monitoring of symptoms and stimulation of early childhood development. The main benefits were believed to be comprehensive care for mother-infant pairs, time-saving and the peer dynamic. The main challenge from the perspective of key informants was the sustainability of dedicating human resources to PNC. Conclusion The PNC model was believed to improve knowledge acquisition, behaviour change and peer support. Participants, staff and the majority of key informants expressed a high level of satisfaction with the PNC model. Sustainability and finding adequate human resources for PNCs remained challenging. Strategies to improve sustainability may include handing over some PNC tasks to members to increase their sense of ownership.