The natural diatomite nanoparticles (Dt) were covalently functionalized by 3-(trimethoxysilyl)-propylamine (MSPA) and salicylaldehyde to support VO(acac)2 and MoO2(acac)2 precursor complexes. The prepared compounds were characterized by FT-IR, PXRD, SEM, EDX, ICP, and BET techniques. Then they were used to catalyze the heterogeneous epoxidation of cis‐cyclooctene as a model alkene using tert-butyl hydroperoxide (TBHP). Various parameters that affect catalytic efficiency were investigated, and the optimized experimental conditions were successfully used for the epoxidation of other linear and non-linear alkenes. The important advantages of these new catalytic systems are their simple preparation, low catalyst loading, and high product yield. Moreover, these catalysts can be used up to three times for an efficient epoxidation of cis‐cyclooctene.