A time-dependent 2-D numerical simulation was performed on a solid oxide iron-air battery (SOIAB) to reveal the fundamental characteristics of this new system. The SOIAB is a rechargeable battery consisting of a solid oxide electrochemical cell (SOEC) and iron as a redox metal. A simple battery configuration was employed assuming a system with a small capacity. A simulation model for a unit element was developed considering heat and mass transfer in the system, taking both electrochemical and redox reactions into account. The numerical results showed the spatial and temporal changes in the temperature field in the charge and discharge operations, which were due to the combined effects of heat generation/absorption by the electrochemical and redox reactions and heat exchange with the air supplied through convective heat transfer. As the reaction rates are functions of the local temperature, the predicted results show the importance of considering the heat transfer phenomena in this system. It was also found that the active reaction region in the redox metal evolves with time. The nonuniform distribution of iron utilization is affected by the effective gas diffusion coefficients in the porous redox metal, and consequently the change in the current density distribution in the SOEC.