Soil pollution by Cr(III) presents a relatively low health risk, since there was a significant toxicological hazard from Cr(III) that can oxidate to Cr(VI) by different oxidant agents in soil. In the light of the significant hazards of Cr(VI), considerable effort has been directed toward understanding the factors that govern the sorption and mobility of Cr(III) in soils and sediments. Hydroxy precipitates of Cr(III) are particularly important because appreciable mobilisation of hydrolysed Cr from montmorillonite occurs only via intercalation into interlamellar space. Although these specific adsorption sites have important implications with respect to environmental quality (e.g. bioavailability, mobility, and the fate of Cr in soils and waters), little information is available in the literature on adsorption of Cr(III) on montmorillonite-humic acid complexes with mixed Al-Fe coprecipitate polynuclear species. In our study we used organo-mineral complexes formed by montmorillonites, in which we intercalated aluminium and iron polymers, complexed with humic acid so as to provide specific adsorption sites. This research aims to establish the sorption trend of the Cr(III) on mixed montmorillonite Al-Fe-humic acid complexes. Batch adsorption studies were carried out to assess the Cr(III) adsorption interactions. The complexes were prepared with 3 mmol of Al or Fe per g of clay. Na-montmorillonite (Mt) and humic acids (HA) were added at pH 5.0 and 7.0, respectively. The adsorption of Cr(III) from aqueous solution of CrCl₃ from 10 to 2038 μmol·l-1 was studied, and the metal amounts in the complexes were analyzed by FAAS and interpreted in terms of the Langmuir equation. The organo-mineral complexes were characterized by DRX, FTIR, TEM and SEM-EDS for mineralogy, elementary analysis and surface area determination. The adsorption trends of Cr(III) on organo-mineral complexes were investigated separately and in all combinations in order to distinguish the effects based on the interactions of the components. Chromium adsorption was studied both in binary (Mt-Al and Mt-Fe) systems and then in the ternary systems (Mt-Al-HA and Mt-Fe-HA). Significant alteration of surface characteristic was observed with TEM and SEM observation, indicating the different influence of Fe and Al on the surface properties of the organo-mineral complexes. The presence of Al or Fe precipitation products causes major changes in the adsorption capacity of Cr(III). The coprecipitated Al or Fe markedly decreased the sorption of Cr(III) in binary systems whereas the strength of chromium intercalation increased in Mt-Al-HA complexes. After Cr(III) adsorption an alteration on the complex surface was observed by SEM, and a significant increase in d(001) spacing on XRD patterns was also detected. The basal spacing of montmorillonite Al-Fe humic acid complexes was increased after Cr(III) adsorption, showing its intercalation. SEM images of the complexes after Cr(III) adsorption points out some important micromorphologic modifications. In particular, SEM observation shows that the Mt-Fe-HA complexes behaved as a non-oriented network, the ferrihydrite suspension was formed by particles of various shapes and dimensions, and the humic acid exhibited a sponge-like structure. The micromorphology of the ferrihydrite–humic acid association was close to that of pure ferrihydrite, while the Mt-Al-HA associations recalled the basic network of smectite. Significant correlation was observed with SEM-EDS in the organo-mineral complexes between adsorbed iron and chromium, indicating the presence of specific sorption sites for this heavy metal. Data presented here, however, show that appreciable immobilisation of adsorbed hydrolysed Cr occurs in organo-mineral complexes. High molecular weight humic acids are effective chelators of sorbed Cr and these ligands may therefore play an important role in the mobilisation and cycling of this metal in soils and sediments. The full potential of native organic ligands to mobilise sorbed Cr can therefore be assessed only after a greater number and variety of organic compounds have been examined.