A one-dimensional unsteady state model is developed for simulation of biomass gasification in a bubbling fluidized bed. The proposed model accounts for the effect of hydrodynamic behavior of the fluidized bed by incorporating the momentum equations of fluid and fuel particles. The model results are validated against experimental data in the literature as well as the results from existing models. The proposed model is capable of predicting the total gas yield and composition of the product gas at different operating conditions. The effect of biomass feeding position is investigated, and the performance of a reactor under nonisothermal conditions is compared with its performance under isothermal operation. As the developed model is computationally less demanding, it can be used to improve design and operational control of bubbling fluidized bed gasifiers.