Nonredox metal ions play significant roles in a wide range of biological and chemical oxidations in which they can modulate the oxidative reactivity of those redox metal ions. With environmentally benign H2O2 as oxidant, the influence of nonredox metal ions on an iron(II) complex mediated olefin epoxidation was investigated through experimental studies and theoretical calculations. It was found that adding nonredox metal ions like Sc3+ can substantially improve the oxygen transfer efficiency of the iron(II) complex toward cyclooctene epoxidation even in the presence of certain amount of water. In O-18-labeling experiments with O-18 water, the presence of Sc3+ provided a higher O-18 incorporation in epoxide. In UV vis studies, it was found that the presence of Sc3+ makes both Fe-v-OOH and Fe-IV=O species unstable. Density functional theory calculations further disclosed that, in the presence of Sc(OTf)(3), the Sc3+ adducts of Fe-IV OOH and Fe-IV=Ospecies are capable of epoxidizing olefin as well as Fe-v=O species, thus opening multiple channels for oxygenation. In particular, in the pathway of cyclooctene epoxidation, the Fe-IV=O/Sc3+ adduct -mediated epoxidation is more energetically favorable than that of the Fe-v=O species (12.2 vs 17.2 kcal/mol). This information may implicate that the presence of certain nonredox metal ions can facilitate these redox metal ions mediating biological and chemical oxidations happening at a relatively low oxidation state, which is more energetically accessible.