A simple and efficient method was used to successfully synthesize novel silver (Ag) nanoparticles immobilized on triethanolamine-functionalized mesoporous silica SBA-15 [SBA-15/IL/Ag]. Its catalytic performance was evaluated in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The structural properties of the synthesized nanocatalyst were characterized using Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and N2 adsorption/desorption isotherms (BET). The catalytic activity of the material during the reduction process was quantitatively monitored using Ultraviolet-Visible (UV-Vis) spectroscopy, which resulted in excellent yields within a short reaction time in aqueous media at room temperature, using a very low catalyst load. A kinetics study was also carried out, which yielded a good rate constant. Moreover, the synthesized nanocatalyst was easily recoverable from the reaction mixture and could be reused multiple times without any significant loss of activity.