The effect of thermal radiation on the two - dimensional, steady-state, coupled heat and mass transfer from a fluid flow to a sphere in the presence of an exothermal catalytic chemical reaction on the surface of the sphere is investigated in the present work. The P1 approximation models the radiative transfer. The finite difference method was used to discretize the mathematical model equations. The discrete equations were solved by the defect correction - multigrid method. The influence of thermal radiation on the sphere surface temperature, concentration and reaction rate was analysed. It was found that, for high values of the radiation conduction parameter, thermal radiation has a significant effect on the surface reaction.