Given advances in care and treatment for HIV, perinatally infected young people are surviving into adolescence. These young people are making decisions about engaging in sexual relationships and it is critical to ensure they have the information they need to engage responsibly in sexual activity, particularly in an era where adherence to treatment could make their virus undetectable. The main objective of this analysis was to examine whether an HIV-positive young person's knowledge about forward transmission is associated with caregiver self-efficacy to talk about sex and general caregiver communication. Using data from a 12-month prospective cohort of caregivers of HIV-positive children aged 9-15 on ART and pre-ART in rural Zimbabwe, we found that caregiver self-efficacy to talk about sex predicted whether conversations about HIV transmission would occur between caregiver and the young person. However, by the end of 12-months, nearly two-thirds of caregivers of HIV-positive teenagers in our sample had still not explained how their adolescents could spread the virus to others despite these caregivers saying their adolescent should know this information at baseline. We discuss the implications for designing sexual and reproductive health (SRH) programs among populations of young people perinatally infected with HIV to ensure that this breakthrough generation receives the SRH support they need.