This paper presents a numerical study that concerning the effect of surface radiation on natural convection cooling of four discrete isoflux heaters flush-mounted on a vertical wall of an air filled rectangular enclosure. The opposite side is isothermally cooled while the top and bottom sides as well as the spacing between the heaters are kept adiabatic. Twodimensional mathematical model was developed based on solving the partial differential equations for the conservation of mass, momentum, and energy. A laminar flow is to be considered in the present model. Galerkin finite element method was utilized for the model formulation. A numerical simulation is carried out to examine the parametric effects of enclosure aspect ratio, Rayleigh number, heater emissivity, adiabatic and cold surfaces emissivities, and the radiation parameter on the role played by the surface radiation in heat dissipation from the discrete heaters in the enclosure. The computed model results were verified through the comparison with those experimental results available in the literature and good agreement between them were noticed. Several correlation equations in terms of aspect ratio, Rayleigh number, heater surface emissivity and the radiation parameter for the average Nusselt number for heaters, its radiative and convective components as well as the maximum surface temperature at the discrete heaters are obtained.