A core–shell Fe3O4@MCM-41-NH2 was synthesized as a magnetic mesoporous nanocomposite was used as an adsorbent for the effective and rapid removal of anionic dye, Congo red. The Fe3O4@MCM-41-NH2 nanocomposites were characterized by FT-IR, SEM, TEM and XRD. The selected removal conditions obtained by a central composite design under response surface methodology were: pH 4.0, mass of adsorbent 0.01 g, stirring time 2.84 min and dye concentration 15 mg L−1. Under these conditions maximum dye removal efficiency obtained was about 95.12%. The adsorption isotherms at different temperatures were fitted well with Langmuir model. Various kinetics models were examined and the results showed that pseudo-second-order could be the best model for the adsorption rate.