Antiretroviral therapy (ART)-readiness counseling has been deemed critical to adherence, instilling knowledge, and promoting positive beliefs and attitudes. In the landscape of changing policy in South Africa, some ART initiators have had prior ART-readiness counseling (e.g., for prevention-of-mother-to-child-transmission [PMTCT] programs). The extent to which previous counseling resulted in retained knowledge and belief is unknown, which may be important to the promotion of women's ART adherence. We compared 320 women living with HIV and initiating ART, with and without prior PMTCT on HIV knowledge, treatment, beliefs, and attitudes. The PMTCT group held more accurate beliefs and more positive attitudes about ART. Both groups lacked understanding of basic HIV biology. Nondisclosure of HIV status was high. Thus, in individuals re-initiating therapy, some knowledge about HIV and its treatment was not well retained. Tailored education and counseling may be critical to adherence, with a focus on biological concepts that impact ART resistance.