Accurate assessment of the potential of a nonisothermal polymer flood process for mobility control requires a model on the viscosities of reservoir fluids as a function of temperature. The temperature dependence of viscosity was included in the reservoir model and an extensive numerical simulation was conducted to examine the effects of temperature-related viscosity model on the reservoir performance during polymer flood in the reservoir with elevated temperature. A three-dimensional numerical model for fluid flow, mass transport, and energy balance is used to analyze the performance of the reservoir operating under polymer flood followed by waterflood. The nonisothermal scheme can be used as a quantitative tool to evaluate the comparative studies of different polymer flooding scenarios with respect to temperature dependence of fluids' viscosities. Results of cumulative oil recovery and water-oil ratio (WOR) at the production well and injectivity at the injection well are presented for various types of temperature dependencies, reservoir temperature, and oil viscosities. The simulation scheme with thermal dependence of fluids' viscosities allows a more quantitative prediction of reservoir performance. Significant improvement in predicted oil recovery and reduction in WOR is obtained for the case of including temperature dependencies of both water and oil because the reduction of oil viscosity is larger than that of brine viscosity. The inclusion of heat loss to over/underburden formations had limited effect on the oil recovery because of relatively small temperature difference under the conditions considered in this study. More rapid reduction of oil viscosity results in the considerable reduction in mobility ratio and significant increase of oil recovery at higher temperature. High oil recovery was obtained with small values of oil viscosity, but the improvement is not proportional to the reduction of oil viscosity.