The effect of reduction temperature on the structure of mesoporous Ni–Fe–Al₂O₃ catalysts and their catalytic activity for the oxidative dehydrogenation of ethane (ODH) have been investigated. Low reduction temperature at 400 °C leads to the reduction of Fe³⁺-based oxides to lower valence FeO_x species, but nickel ions in the [–Ni–O–Al–] framework cannot be reduced at this temperature. These highly dispersed Ni²⁺-based oxide and FeO_x species with close proximity contribute to ethane dehydrogenation and N₂O decomposition, respectively. When the reduction temperature is increased to 600 °C, a continuous reduction and migration of Ni²⁺ from the bulk phase to the surface took place, forming 5–6 nm isolated metallic Ni nanoparticles, which resulted in a decrease in catalyst activity under this condition. Thus, highly dispersed Ni²⁺-based oxide and FeO_x species with close proximity effectively contribute to the selective conversion of ethane to ethylene.