Background: The relationship between concurrent sexual partnerships and HIV risk is not fully understood. Evidence on the relationship between partner concurrency (one's sexual partner has another partner) and individual HIV risk is limited. In this study, the relationship between reported sexual partner concurrency and the risk of HIV infection was explored among South Africans. Methods: Data from the third South African national HIV survey were used. In this survey, performed in 2008, questionnaires and HIV tests were administered to a nationally representative sample of 15 031 persons. Bivariate analysis and multiple logistic regression were used to evaluate the relationship between partner concurrency and HIV serostatus. Spearman's correlation was used to test the association between the prevalence of HIV and partner concurrency by race in women. Results: The relationship between HIV prevalence and partner concurrency varied by race. At a cross-racial level there was a positive association between HIV prevalence and partner concurrency for women (rho = 0.95, p = 0.05). Among coloured, white, and Indian persons, HIV prevalence and partner concurrency rates were too low to allow further statistical testing. In the bivariate analysis, black African women who reported partner concurrency had a higher prevalence of HIV (36% (95% confidence interval (CI) 29.7–42.0) vs. 23% (95% CI 19.6–26.1), p