A CaO/Fe3O4 nanocomposite was modified by sodium dodecyl sulfate (SDS) and used for Cr(III) removal from aqueous solution. The physical and surface characteristics of the adsorbent were studied by different analysis techniques. The effects of key parameters such as pH, contact time, temperature, initial concentration of Cr(III) ions, and adsorbent dose were investigated at a fixed mixing rate. Parameters were optimized to attain the best possible removal efficiency of Cr(III) ions. The maximum adsorption capacities obtained from the Langmuir model were determined. The results of equilibrium and kinetic studies indicate that the adsorption process follows the Langmuir isotherm model and the pseudo-second-order kinetic model. The thermodynamic study demonstrated that the adsorption process was suitable, spontaneous, and exothermic.