The elimination of iodide (I⁻) from water is a tough subject due to its low adsorption tendency and high mobility. In this work, MCM-41/Ag₂O nanomaterials were prepared, characterized, and employed to adsorb I⁻ from water. The Ag₂O nanoparticles were dispersed homogeneously in the pores or at the surface of the MCM-41 support, and the Ag₂O nanoparticles in the pores had small particles sizes due to the confinement of the mesoporous channel. The prepared MCM-41/Ag₂O nanomaterials exhibited a higher specific surface area than previously reported Ag₂O-based composites. The adsorption of I⁻ by the nanomaterials was able to reach equilibrium at 180 min. The MCM-41/Ag₂O nanomaterials showed a better adsorption capacity per unit mass of Ag₂O than pure Ag₂O nanoparticles and previously reported Ag₂O-based composites prepared using other supports. Furthermore, the MCM-41/Ag₂O nanomaterials exhibited high selectivity for I⁻ in the presence of high concentrations of competitive anions, such as Cl⁻ or Br⁻, and could function in a wide range of pH. The chemical reaction between Ag₂O and I⁻ and the surface adsorption were the main adsorption mechanisms. These results indicate that MCM-41/Ag₂O nanomaterials are a promising and efficient adsorbent material suitable for the removal of I⁻ for practical application.