The covalent immobilization of Mn(III)-Salen complexes on an amorphous mesoporous silica support is reported. Both (3-aminopropyl)trimethoxysilane (APTMS) and (3-iodopropyl)trimethoxysilane (IPTMS) were used in a post-synthesis grafting method to prepare organosilane-modified porous materials. Peptide and ester interactions were employed to anchor the Salen complex to the silica framework. The catalytic activity of the immobilized Salen catalyst was studied by epoxidation of cyclooctene. The comparison of the homogeneous and the immobilized catalyst shows that there was no significant loss of catalytic activity for epoxidation by immobilization. In the current study, the effects of reaction temperatures, solvents, and amount of catalyst on the catalytic activity were investigated. The optimal yield of cyclooctene oxide was obtained at 45°C using toluene as the solvent.