Background: The effectiveness of the rotavirus vaccine under conditions of routine use in an African setting with a high prevalence of HIV infection needs to be established. We assessed the vaccine effectiveness of monovalent human rotavirus vaccine in preventing admission to hospital for acute rotavirus diarrhoea, after its introduction at age 6 and 14 weeks into South Africa's national immunisation programme. Methods: This case-control study was done at seven hospitals in South Africa between April 19, 2010, and Oct 31, 2012. The hospitals were located in a range of urban, peri-urban, and rural settings, with varying rates of population HIV infection. Cases were children aged from 18 weeks to 23 months who were age-eligible to have received at least one dose of the human rotavirus vaccine (ie, those born after June 14, 2009) admitted to hospital with laboratory-confirmed acute rotavirus diarrhoea, and the primary control group was children admitted to hospital with diarrhoea testing negative for rotavirus. A second control group comprised children admitted to a subset of three of the seven hospitals with respiratory illness. The primary endpoint was adjusted vaccine effectiveness (1 - adjusted odds ratio × 100%) in children aged from 18 weeks to 23 months and was calculated by unconditional logistic regression. This study is registered on the South African National Clinical Trial Register, number DOH-27-0512-3247. Findings: Of 540 rotavirus-positive cases, 278 children (52%) received two doses, 126 (23%) one dose, and 136 (25%) no doses of human rotavirus vaccine, compared with 1434 rotavirus-negative controls of whom 856 (60%) received two doses, 334 (23%) one dose, and 244 (17%) no doses. Adjusted vaccine effectiveness using rotavirus-negative controls was 57% (95% CI 40-68) for two doses and 40% (16-57) for one dose; estimates were similar when respiratory controls were used as the control group. Adjusted vaccine effectiveness for two doses was similar between age groups 18 weeks-11 months (54%, 95% CI 32-68) and 12-23 months (61%, 35-77), and was similar in HIV-exposed-uninfected (64%, 95% CI 34-80) and HIV-unexposed-uninfected children (54%, 31-69). Interpretation: Human rotavirus vaccine provided sustained protection against admission to hospital for acute rotavirus diarrhoea during the first and second years of life. This finding is encouraging and establishes the public health value of rotavirus vaccine in an African setting, especially as rotavirus vaccines are introduced into an increasing number of African countries.