The introduction of routine HIV counselling and testing (HCT) has increased the number of pregnant women being tested and receiving prevention of mother to child transmission of HIV (PMTCT) interventions in South Africa. While many women may enroll in PMTCT, there are barriers that hinder the success of PMTCT programmes. The success of the PMTCT is dependent on the optimal utilization of PMTCT interventions which require the support of the woman's partner, and other members of her family. We conducted focus groups interviews with 25 HIV-positive post-natal women enrolled in PMTCT, in the City of Tshwane, South Africa. The study explored HIV-positive status disclosure to partners and significant family members and assessed the effect of nondisclosure on exclusive infant feeding. Most women disclosed to partners while few disclosed to significant family members. Most women initiated mixed feeding practices as early as one month and reported that they were pressurized by the family to mix feed. Mixed feeding was common among women who had not disclosed their HIV-positive status to families, and women who had limited understanding of mother to child transmission of HIV. Women who disclosed to partners and family were supported to adhere to the feeding option of choice. Health providers have a critical role to play in developing interventions to support HIV pregnant women to disclose in order to avoid mixed feeding. Improving the quality of information provided to HIV-positive pregnant women during counselling will also reduce mixed feeding.