Thallium (Tl) is highly toxic to living organisms. The major sources of Tl released into the environment are mainly ore mining and high technology industries. So far, the environmental fates of thallium have not been well understood. Clay minerals are one of the important colloid constituents in soils and play an important role in determining the adsorption of metals by soils. Thus, this study investigated the Tl(I) adsorption and desorption mechanisms of 2:1 clay minerals, in hope, to bring insights into the interactions of thallium with soils. The adsorption and desorption experiments of Tl(I) were conducted for vemiculite, montmorillonite, and illite, which have different structural charge properties. The results of adsorption experiment revealed that Tl(I) adsorption capacities of the clay minerals followed the order of vermiculite＞montmorillonite>illite. The degree of hysteresis followed the order of illite＞vermiculite＞montmorillonite. Thus, the adsorption of Tl(I) on clay minerals is significantly influenced by the charge properties of the clay minerals. The negative charges of vermiculite and illite mainly locate at the tetrahedral sites, whereas those of montmorillonite mainly occur at the octahedral site. The location and density of negative charges in the structures of these clay minerals leads to different binding affinities of these clay minerals toward Tl(I) ions. Consequently, these minerals were different in terms of the Tl(I) adsorption capacity and adsorption/desorption hysteresis. As Tl(I) is fixed into the interlayer sites of vermiculite and illite, the adsorbed Tl(I) on these minerals are therefore more difficult to be desorbed. Comparatively, Tl(I) adsorption on montmorillonite is more reversible. Because vermiculite and illite exhibit a high adsorption capacity and a high adsorption irreversibility of Tl(I), the mobility of Tl(I) in the soils containing these two clay minerals is expected to be relatively low due to the strong retention of Tl(I) by these minerals in the soils. Comparatively, when montmorillonite is the predominant clay component of soils, the mobility of Tl(I) in the soils is expected to be relatively high due to the reversible Tl(I) adsorption of montmorillonite in the soils. Therefore, the mobility and bioavailability of Tl(I) in a soils may be determined by the characteristics of clay minerals in the soil, which can be used to assess the risk of Tl(I) pollution to ecosystems and public health.