This dataset contains free residual chlorine, turbidity, nitrate, chloride, sulphate, fluoride, phosphate and thermatolerant coliform concentrations in groundwater from a variety of sources within two neighbourhoods of Kisumu, Kenya. A total of 73 groundwater sources were tested between February and March 2014. The data were collected as part of the Groundwater2030 project, which aims to reduce the health problems that result from consumption of contaminated groundwater in urban areas of Africa. The project was co-ordinated by the University of Southampton, with partners at the University of Surrey, the Victoria Institute of Research on Environment and Development (VIRED) International, and the Jaramogi Oginga Odinga University of Science and Technology. The project was funded by the Natural Environment Research Council and the Department for International Development as part of the Unlocking the Potential of Groundwater for the Poor (UPGro) programme. Full details about this dataset can be found at https://doi.org/10.5285/4062e6d9-2e90-4775-87f1-179dea283ef1