Chemical reactivity of LaNi0.6Fe0.4O3 (LNF) with Cr2O3 has been investigated in order to examine the long-term stability of the LNF phase at 1073 K, which shows a high performance as the cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The chemical stability of LNF was compared with that of La0.8Sr0.2MnO3 (LSM) under the existence of Cr2O3. The LNF powder, a powder mixture of LNF and Cr2O3, and a powder mixture of LSM and Cr2O3 were, respectively, heated at 1073 K, and they are analyzed by X-ray powder diffraction with the Rietveld refinement. We found that the LNF phase maintains the hexagonal crystal system heated in air up to 1000 h. In the LNF-Cr2O3 mixture, the LNF phase kept its pristine crystal structure while a new phase, NiCr2O4, was detected, which was produced by the reaction between Cr2O3 and the residual NiO contained in the starting LNF powder. In the LSM-Cr2O3 mixture, LSM reacted with Cr2O3 and produced a significant amount of MnCr2O4. LNF showed a much better chemical stability against Cr2O3 than LSM. LNF can serve as a long-life cathode in the IT-SOFC system.