Polycrystalline Lu 3 Fe 5 O 12 , prepared using the solid state reaction method, has Fe in the mixed valence state as inferred from the X-ray photoelectron spectroscopy. A spectral change in the impedance plot at 343 K is attributed to metal-like to insulator transition (MIT), which is analyzed in terms of localized and delocalized eg electrons. The change in the slope at 343 K in the DC conductivity plot also proves the MIT. The dependence of Z′ on temperature and Z″ on frequency clearly substantiates the presence of localized electrons up to 343 K and delocalized electrons above 343 K.