It is expected that new projects for the exploitation of lithium (Li) will emerge in the coming years, due to its growing importance in the energy transition. Facing environmental concerns, it is therefore important to evaluate the influence of mining activity on the quality of groundwater, soils and crops grown around the exploitation areas. Portugal is one of the European countries with higher lithium hard-rock resources. The aim of this study is determining Li concentration in the edible tissues of Brassica oleracea (known as cabbage) and evaluate, together with the drinking water ingested, the population’s exposure dose to this element and if it represents any health risks. A total of twenty-four sampling sites were selected on farms and in kitchen gardens located near and far from a Portuguese active mine (C-57 Castanho, Guarda). Here an aplite-pegmatite of the lithium-cesium-tantalum type family has been exploited for long time. The mined raw materials (quartz-feldspars-lepidolite) are mainly used in the ceramic industry. The soil pH and concentrations of Li in the edible parts of the crop and in the irrigation and drinking water were analyzed. The Li concentrations in the samples were determined by ICP-MS and the vegetables tissues analysis was preceded by microwave-closed vessel acid digestion (aqua regia). Analytical procedures were conducted following quality requirements described in ISO/IEC17025:2017 standard. The Li concentrations detected in the irrigation water (2.4–36.6 μg/L), drinking water (1–87.2 μg/L) and cabbage (34–1627 μg/kg fresh weight) showed the influence of the distance from the mining works (maximum 0.5–1.5 and 2–8 km, respectively). The soils where the crop grows are acid to sub-alkaline (pH H2O between 4.6 and 7.9), and soil pH is not well correlated with Li in the crop. The Li exposure dose, estimated only from the consumption of cabbage from the sampling sites and the ingestion of drinking water (from private wells and public supply), evaluated according to the local diet habits, indicates that the owners of the farms/kitchen gardens are not likely exposed to health risks. This evaluation considered the available provisional oral reference dose of 2 μg/kg day, indicated by USEPA in 2008, based on a steady-state plasma Li concentration of 4.2 mg/L. This research is ongoing on other Portuguese mining areas and with other crops, under the project ILiFood (EXPL/CTA-AMB/0977/2021).