Fe25Cr5Al alloys with and without rare earth (RE) elements La and Ce, namely Fe25Cr5Al-RE and Fe25Cr5Al alloys, were prepared and isothermal oxidation tests were conducted at 1100 °C. The morphology of oxide scale was observed by scanning electron microscope (SEM), and the oxidation product was identified by energy disperse spectroscopy (EDS) coupled with X-ray diffraction (XRD). Results show that after oxidation for 1, 20, and 300 h, the mass gain of Fe25Cr5Al alloys is 0.08, 0.84, and 4.41 mg·cm^-2, but that of Fe25Cr5Al-RE alloys is 0.03, 0.35, and 0.92 mg·cm^-2, respectively. The oxide scale of the two alloys consists of α-Al₂O₃. La and Ce promote the formation of compact and continuous oxide scale, which significantly improves the high temperature oxidation resistance of Fe25Cr5Al alloys. Moreover, RE oxide pegs can be observed at substrate/scale interface of Fe25Cr5Al-RE alloys, which makes the bond between substrate and scale tighter, thus enhancing the adhesion of the interface. There are RE oxides in oxide scale of Fe25Cr5Al-RE alloys, which effectively inhibits further oxidation of the alloys.