One Achilles' heel of post-Apartheid South Africa is the growing intra-racial income inequality, particularly among Africans. This paper examines the role of labour unions in explaining this phenomenon among African men given that labour markets are at the core of income inequality in South Africa. Using cross-sectional data drawn from Labour Force Surveys for 2001–10, we find a monotonically declining union wage premium. Further, our results indicate that unions have both compressionary and disequalising effects on wages. The disequalising effect dominates the compressionary effect, suggesting that unions have a net effect of increasing wage inequality among African men in South Africa. This finding implies that there is scope for unions to reduce inequality through initiatives that promote wage compression.