Tetragonal perovskite phase Ce0.9Ca0.1AlO2.95 + x was obtained for the first time. Such phase, containing cerium in the oxidation state of 3+, can be promising anode materials for a solid oxide fuel cells (SOFCs). Ce0.9Ca0.1AlO2.95 + х (space group I4/mcm) was synthesized by the solid-phase method at 1400°С in a nitrogen flow with using ammonium oxalate (NH4)2C2O4 to create a reducing atmosphere. Thermogravimetry results showed that Ce0.9Ca0.1AlO2.95 + x was stable to oxidation up to 500°С in air and up to 700°С in argon (partial pressure of oxygen рО2 = 10−4 bar). The thermal expansion coefficient measured by dilatometry was equal to 11.16·10−6 К−1. The temperature dependences of the electrical conductivity (for undoped phase CeAlO3 σ ≈ 1·10−3 S/cm and for doped Ce0.9Ca0.1AlO2.95 + x σ ≈ 3·10−2 S/cm at 500°С in air) were obtained by the electrochemical impedance spectroscopy measurements). The electrical conductivity of these samples at the temperatures range of 350–500°С was almost independent of the partial pressure of oxygen рО2 from 10−18 to 0.21 bar, however, there was a slight negative slope at T > 500 °C (рО2). The total ionic transport numbers measured by the EMF method were close to 1·10−3, which indicated the dominance of electronic conductivity. The measurement of the sign of the thermal-EMF showed that positive charge carriers (holes) were dominant charge carriers. © 2023 Hydrogen Energy Publications LLC.