Risky sexual behavior exposes young adults to poor reproductive health outcomes. Parental social support is associated with reduced incidence of risky sexual behavior, but this association has not been adequately investigated in South Africa. We used data from Waves 1 and 3 of the Cape Area Panel Study (a longitudinal study of adolescents and young adults aged 14-22 years and living in the Cape Town metropolitan area) to investigate the associations between parental social support and young adult risky sexual behavior in South Africa. We conducted multivariable logistic regression analyses to assess whether lack of specific categories of parental social supports at wave 1 (baseline) are associated with higher risky sexual behaviors by young adults at wave 3 (follow-up). We found that young adults who never ate meals with their mothers and those who never discussed personal matters with their fathers had increased risks of multiple sexual partnerships. Also, young adults who never got pocket money or money for gifts from their mothers had increased risk to engage in unprotected sex during their first sexual encounter. Our findings suggest that eating family meals, discussing personal matters with youth, and providing them with pocket money, may protect young adults in South Africa from risky sexual behavior.