There has been substantial research on the sources and geochemical processes associated with fluoride (F-) in agricultural groundwater. However, the spatial distribution, geochemical behaviours, and enrichment mechanisms of fluoride in the groundwater from a coal-mining district used for drinking water supply have not been fully understood. In this study, 42 drinking water samples of the groundwater were collected in May 2019 and March 2020 from the Sulin coal-mining district, Anhui, China. Samples were analysed to investigate the distribution, geochemical behaviour, and formation mechanisms of fluoride. The F- concentrations in the groundwater samples ranged from 0.55 to 2.06 mg/L, with a mean value of 1.16 mg/L. The F- concentrations in 54.76% of the water samples exceeded China’s national standards (1.00 mg/L). The results show that the F- in the water was enriched in an environment with high pH and HCO₃ - content. The weathering of F- bearing minerals was the main source of F- in the drinking water supply. Evaporation, cation exchange, competitive effect, and anthropogenic activities were considered to have promoted elevated F- concentrations in the groundwater resource. This research will aid policy development for properly managing drinking water to eliminate health problems in coal-mining districts due to excessive fluoride intake.