Aluminosilicate (Al-MCM-41) was synthesized via a modified wet-method in a Si/Al atomic ratio of 13.64:1.00 and calcination at 500 °C. The structural as well as the thermal stability were studied by powder X-ray diffractometry (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), Fourier transform infrared (FTIR) analysis and surface area measurements. Al-MCM-41 was confirmed to acquire a mesoporous structure with a high stability against hydrolysis which was attributed to the homogeneous dispersion of Al(III) in the silica framework. The adsorption parameters of the cationic dye methylene blue (MB), on Al-MCM-41 were investigated in aqueous solutions. The adsorption isotherm data showed a notable monolayer adsorption capacity (285 mg g⁻¹) of MB and fitted well the Langmuir adsorption model and the pseudo-second-order kinetics model. The adsorbent was applied successfully for removing 92.0–94.7% of MB from spiked fresh water samples and the initial capacity was recovered by 0.05 mol L⁻¹ HCl or calcination.