Complex cluster $[\mathrm{Ti}{\mathrm{O}}_5\cdot V_{\mathrm{O}}^z]$ and $[\mathrm{Sr}{\mathrm{O}}_{11}\cdot V_{\mathrm{O}}^z]$ (where $V_{\mathrm{O}}^z=V_{\mathrm{O}}^X$ , $V_{\mathrm{O}}^{•}$ , $V_{\mathrm{O}}^{••}$ ) vacancies were identified in disordered $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ powders prepared by the polymeric precursor method, based on experimental measurements by x-ray absorption near edge structure spectroscopy. The paramagnetic complex states of $[\mathrm{Ti}{\mathrm{O}}_5\cdot V_{\mathrm{O}}^{•}]$ and $[\mathrm{Sr}{\mathrm{O}}_{11}\cdot V_{\mathrm{O}}^{•}]$ with unpaired electrons were confirmed by electron paramagnetic resonance spectroscopy. The disordered powders showed strong photoluminescence at room temperature. Structural defects of disordered powders, in terms of band diagram, density of states, and electronic charges, were interpreted using high-level quantum mechanical calculations in the density functional framework. The four periodic models used here were consistent with the experimental data and explained the presence of photoluminescence.