Recent advances in dense, multiphase, computational fluid dynamics (CFD) have allowed accurate simulation of the gas and particle motion in bubbling and circulating fluidized beds. Since fluidized-bed reactors are used for many chemical processes, a simulation must also be able to accurately couple chemical reactions to bed hydrodynamics. The catalytic decomposition of ozone (O-3) often has been used to study experimentally the contacting behavior of catalytic reactors. Simulations of laboratory-scale experiments of premixed O-3 decomposition in a bubbling fluidized bed using the multiphase CFD code MFIX were conducted. The grid-independent results are in very good agreement with reported experimental data on total conversion over a range of fluidization velocities and initial bed heights. This confirms the ability of multiphase hydrodynamic models to capture quantitatively the effect of hydrodynamics on chemical reactions in a bubbling fluidized bed.