We report herein for the first time a facile synthesis method to obtain SrTi_1−xFe_xO₃ nanocubes by means by a microwave-assisted hydrothermal (MAH) method at 140 °C. The effect of iron addition on the structural and morphological properties of SrTiO₃ was investigated. X-ray diffraction measurements show that all STFO samples present a cubic perovskite structure. X-ray absorption spectroscopy at Fe absorption K-edge measurements revealed that iron ions are in a mixed Fe²⁺/Fe³⁺ oxidation state and preferentially occupy the Ti⁴⁺-site. UV-visible spectra reveal a reduction in the optical gap (E_gap) of STFO samples as the amount of iron is increased. An analysis of the data obtained by field emission scanning electron microscopy points out that the nanoparticles present a cubic morphology independently of iron content. According to high-resolution transmission electron microscopy results, these nanocubes are formed by a self-assembly process of small primary nanocrystals.