An homogenous intercalated compound of dioctahedral 1:1 clay mineral with cesium chloride was prepared by immersing an homogeneous 8.4 Å hydrated nacrite in a CsCl-saturated solution. The nacrite/CsCl complex obtained was studied using X-ray diffraction and thermogravimetric analysis (TGA). The best agreement between the observed and the simulated ρ(z) (R = 7%) was obtained with one Cl– ion, one Cs+ ion and one water molecule (per half-unit cell). The cation was located near the oxygen atom plane, while the anion was located near the hydroxyl groups of the adjacent layer. The number of the species intercalated in nacrite/CsCl was confirmed by TGA analysis. The best agreement between the calculated and the experimental hkl reflections, with h and/or k ≠ 0, corresponded to a stacking of 70% and 30% for T1 = –0.35a – 0.20b + 10.50n and T2 = +b/3 + 10.5n, respectively. These results indicate that the surface hydroxyls form hydrogen bonds with Cl– ions. The Cs+ ions are situated near the ditrigonal cavities of the tetrahedral sheet and they interact with the surface oxygen atoms whereas the H2O molecules interact with the intercalated species.