A three-dimensional numerical simulation of the solid oxide fuel cell (SOFC) anode overpotential is conducted in a microstructure which is reconstructed by dual-beam focused ion beam–scanning electron microscopy (FIB-SEM). Gaseous, ionic, and electronic transport equations are solved by a lattice Boltzmann method with electrochemical reaction at the three-phase boundary. The predicted anode overpotential agrees with the experimental data at the fuel supply of, while it is larger than the data at. The dependence of exchange current density on steam partial pressure, gas diffusion modeling, as well as computational domain size must be further investigated in the future. Local three-dimensional distributions of electrochemical potential and current density inside the anode microstructure are obtained. Their nonuniformities are attributed to the scattered three-phase boundaries and complex transport paths through the solid phases.