Two Fe–1.5wt.%Mo powdered alloys modified with 1.5wt.%SiO₂ and 1.5wt.%TiO₂ compacted through spark plasma sintering have been studied. Transmission electron microscopy was used to characterize the nano-scale microstructure. The results showed that sintered FeMo+SiO₂ powder is able to keep a nanometric scale grained structure up to a sintering temperature of 815°C. Mean grain size of the FeMo+TiO₂ compacted powder maintained its nanometric range up to 900°C. Residual porosity decorates the grain boundary and the triple grain junctions in all the studied sintering conditions. Moreover, nano-porosity accounted for a maximum of 0.26% volume fraction. Direct comparison between X-ray diffraction grain size evaluation (from previously published data) and transmission electron microscopy investigations, showed a significant underestimation when using the first approach. Nano-indentation tests confirmed that the micro-hardness values tend to increase with sintering temperature. Berkovich nano-indentation tests clearly showed that micro-hardness values in nanostructured compacts lead to overestimation of the real hardness values.