New nanocomposite ceramic electrolytes with enhanced conductivity at low temperatures have been mechanically prepared based on Li2SO4–Fe2O3 system. Nanocomposites with filler concentrations of x = 0.1-0.5 have been studied by impedance spectroscopy and thermal analysis in the temperature range of 200–500oC. Unusual dependence of the conductivity on increasing Fe2O3 content has been noted: both the ionic conductivity (σ) below a transition temperature at about Tt = 350oC, as well as this temperature, increase. A step change to lower values is observed in the dc-conductivity date at Tt which also increases with the Fe2O3 content. However, above Tt the temperature dependence of σ is almost independent of the oxide concentration. This thermal behavior of Li-ion transport is attributed to lattice defects generation in Li2SO4 with increasing the content of dispersed Fe2O3 nanoparticles below Tt. However, above Tt, the results indicate that the nanoparticles no longer affect Li-ion transport.