The environmental pollution by ecotoxic metals is a problem of increasing significance for ecological/human health reasons. Among these elements, cadmium is of special concern due to its high mobility in the soil/plant system and acute toxicity. To limit Cd contamination in plants, and to enhance food safety, it is critical to understand Cd biogeochemical cycle, in particular what controls the bioavailability of this element. Previous studies have demonstrated that Cd bioavailability in soils depends ultimately on its chemical speciation. It has been proposed that non-protein thiols and organic acids play a major role in cadmium phytoavailability and distribution in plants. In the Cd-(hyper)accumulator Solanum nigrum and non-accumulator Solanum melongena, the role of these organic ligands in the accumulation and detoxification mechanisms of Cd are debated. Here, we used X-ray absorption spectroscopy to investigate Cd speciation in these plants (roots, stem, leaves) and in the Cd-doped soils used for their culture to unravel the plants responses to Cd exposure. In both S. nigrum and melongena, Cd in roots and fresh leaves is mainly bound to thiol ligands, with a small contribution of inorganic S ligands in S. nigrum leaves. We interpret the Cd binding to sulfur ligands as detoxification mechanisms, possibly involving the sequestration of Cd complexed with glutathione or phytochelatins in the plant vacuoles. In the stems, results show an increase binding of Cd to -O ligands (>50% for S. nigrum). We suggest that Cd is partly complexed by organic acids for transportation in the sap. To further constrain the fate of Cd, we performed Cd stable isotope analysis. Our results show that, similarly to Zn, Cd isotopes are fractionated upon roots uptake – with depleted values in the roots. The stems display heavier values than both roots and leaves, which are consistent with ab initio isotope fractionation predictions for Cd between -O and -S ligands, which suggest Cd isotopes could be used to probe Cd speciation in natural samples.