OBJECTIVE South African adolescents have high HIV risk, yet few prevention interventions are effective. Parents play a pivotal role in youths' healthy sexual development and may be at risk themselves. We tested whether Let's Talk!, a worksite-based parenting program, improves parent-child communication about HIV and sexual health and parent condom use self-efficacy and behavior. METHODS We culturally adapted Let's Talk! in two languages, drawing on formative research and community stakeholder input. We then conducted a small randomized test at a large public worksite in Cape Town, South Africa. The intervention consisted of 5 weekly 2-hour group sessions for parents of youth aged 11-15. Sixty-six parents (64% female) and their 64 adolescents (41% female) completed surveys before and 1-2 weeks post-intervention; surveys assessed comfort with talking about sex, communication about 16 HIV- and sex-related topics, and parents' condom use self-efficacy and behavior. Thirty-four black African (Xhosa language) and 32 coloured (mixed-race; Afrikaans language) parent-child dyads participated. Parents were randomized to intervention (n = 34) and control (n = 32) groups; randomization was stratified by language. RESULTS Multivariate regressions indicated that the intervention significantly increased parents' comfort with talking to their adolescent about sex, b(SE) = .98(.39), p = .02, and the number of sex- and HIV-related topics discussed with their adolescent, b(SE) = 3.26(1.12), p = .005. Compared with control parents, intervention parents were more likely to discuss new sex- and HIV-related topics not discussed before the intervention, b(SE) = 2.85(.80), p <.001. The intervention significantly increased parents' self-efficacy for condom use, b(SE) = .60(.21), p = .007. CONCLUSIONS Let's Talk! holds promise for improving parent-child communication, a critical first step in preventing HIV among youth.