A three-dimensional (3D) nonisothermal model is developed and applied for anode-supported planar solid oxide fuel cell (SOFC). The mass and momentum, species, ion, electric, and heat transport equations are solved simultaneously by implementing the electrochemical kinetics and electrochemical reaction as volumetric source terms. The interconnect land limits the O-2 transport under the land and lowers the local current density under the land. The effects of interconnect land width and cathode substrate thickness on SOFC cell performance are quantified in this study. Cathode stoichiometry is found to have a large effect on the SOFC cell temperature distribution. Under low-cathode stoichiometry, significant temperature gradients are seen in the SOFC cell. Higher-cathode stoichiometry is beneficial for lower temperature and more uniform current density distribution in SOFC cell. Co-flow and counter-flow arrangements are investigated and discussed with the model. Counter-flow arrangement is found to induce a high temperature and high current density region near the H-2 inlet. On the other hand, co-flow arrangement leads high temperature and high current density to occur relatively downstream, a slightly lower maximum temperature on cell and considerably more uniform current density distribution. A 67.2-cm(2) SOFC cell is simulated considering the side cooling effect. The side cooling effectively lowers the cell temperature, at the same time, causes temperature, current density, and fuel utilization nonuniformity in the across multichannel direction. Because of the strong coupling of the in-plane current density distribution and temperature distribution, limiting the locally high temperature and temperature gradient is critical for achieving a more uniform current density distribution in anode-supported planar SOFC.