A dynamic mathematical model of a continuous atmospheric bubbling fluidized bed combustor (ABFBC) has been developed on the basis of first principles and used to correlate data from a pilot-scale combustor, The model accounts for bed and freeboard hydrodynamics, volatiles release and combustion, char particles combustion and their size distribution, and heat transfer. The solution procedure of dynamic model employs method of lines (MOL) approach for the solution of the governing nonlinear partial differential equations. The initial conditions required for each sub-model was provided from the simultaneous solution of governing equations of dynamic model with all temporal derivatives set to zero. Predictive accuracy of both steady state and dynamic models was assessed by applying it to the prediction of the behavior of METU 0.3 MW ABFBC Test Rig, and comparing their predictions with measurements taken on the same rig at steady state and transient conditions. Transient data were obtained by imposing changes to coal and air flow rates and measuring corresponding changes in oxygen and carbon monoxide concentrations at the exit of freeboard and in temperatures along the combustor against time. Comparisons of measurements and predictions chow that the predictions of the model are physically correct and agree well with the measurements.